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Today's business enterprises must deal with global competition, reduce the cost of doing business, and rapidly develop new services and products. To address these requirements enterprises must constantly reconsider and optimize the way they do business and change their information systems and applications to support evolving business processes. Workflow technology facilitates these by providing methodologies and software to support (i) business process modeling to capture business processes as workflow specifications, (ii) business process reengineering to optimize specified processes, and (iii) workflow automation to generate workflow implementations from workflow specifications. This paper provides a high-level overview of the current workflow management methodologies and software products. In addition, we discuss the infrastructure technologies that can address the limitations of current commercial workflow technology and extend the scope and mission of workflow management systems to support increased workflow automation in complex real-world environments involving heterogeneous, autonomous, and distributed information systems. In particular, we discuss how distributed object management and customized transaction management can support further advances in the commercial state of the art in this area.
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Distributed and Parallel Databases, 3, 119-153 (1995)
©Kluwer Academic Publishers, Boston. Manufactured in The Netherlands.
An Overview of Workflow Management:
From Process Modeling to Workflow Automation
Infrastructure
DIIMITRIOS GEORGAKOPOULOS AND MARK HORNICK {dimitris,mfh0}@gte.com
GTE Laboratories Incorporated, 40 Sylvan Road, Waltham, MA 02254
AMIT SHETH amit@cs.uga.edu
University of Georgia, LSDIS Lab, Department of C.S., 415 GSRC, Athens, GA 30602
Abstract. Today’s business enterprises must deal with global competition, reduce the cost of doing business, and
rapidly develop new services and products. To address these requirements enterprises must constantly reconsider
and optimize the way they do business and change their information systems and applications to support evolv-
ing business processes. Workflow technology facilitates these by providing methodologies and software to sup-
port (i) business process modeling to capture business processes as workflow specifications, (ii) business process
reengineering to optimize specified processes, and (iii) workflow automation to generate workflow implementa-
tions from workflow specifications. This paper provides a high-level overview of the current workflow manage-
ment methodologies and software products. In addition, we discuss the infrastructure technologies that can
address the limitations of current commercial workflow technology and extend the scope and mission of work-
flow management systems to support increased workflow automation in complex real-world environments
involving heterogeneous, autonomous, and distributed information systems. In particular, we discuss how dis-
tributed object management and customized transaction management can support further advances in the com-
mercial state of the art in this area.
Keywords: BUSINESS PROCESS RE-ENGINEERING, WORKFLOW SYSTEMS, CUSTOMIZED
TRANSACTION MANAGEMENET
1. Introduction
The workflow concept has evolved from the notion of process in manufacturing and the
office. Such processes have existed since industrialization and are products of a search to
increase efficiency by concentrating on the routine aspects of work activities. They typi-
cally separate work activities into well-defined tasks, roles, rules, and procedures which
regulate most of the work in manufacturing and the office. Initially, processes were carried
out entirely by humans who manipulated physical objects. With the introduction of infor-
mation technology, processes in the work place are partially or totally automated by infor-
mation systems, i.e., computer programs performing tasks and enforcing rules which were
previously implemented by humans.
Medina-Mora et al. [32] categorize processes in an organization into material pro-
cesses, information processes, and business processes. The scope of a material process is
to assemble physical components and deliver physical products. That is, material pro-
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cesses relate human tasks that are rooted in the physical world. Such tasks include, mov-
ing, storing, transforming, measuring, and assembling physical objects.
Information processes relate to automated tasks (i.e., tasks performed by programs) and
partially automated tasks (i.e., tasks performed by humans interacting with computers)
that create, process, manage, and provide information. Typically an information process is
rooted in an organization’s structure and/or the existing environment of information sys-
tems. Database, transaction processing, and distributed systems technologies provide the
basic infrastructure for supporting information processes.
Business processes are market-centered descriptions of an organization’s activities,
implemented as information processes and/or material processes. That is, a business pro-
cess is engineered to fulfill a business contract or satisfy a specific customer need. Thus,
the notion of a business process is conceptually at a higher level than the notion of infor-
mation or material process. In this paper, we focus on business processes that are primarily
implemented as information processes.
Once an organization captures its business in terms of business processes, it can reengi-
neer each process to improve it or adapt it to changing requirements. Reasons cited for
business process redesign include increasing customer satisfaction, improving efficiency
of business operations, increasing quality of products, reducing cost, and meeting new
business challenges and opportunities by changing existing services or introducing new
ones. Business process reengineering involves explicit reconsideration and redesign of the
business process. It is performed before information systems and computers are used for
automating these processes. Information process reengineering is a complementary activ-
ity of business process reengineering. It involves determining how to use legacy and new
information systems and computers to automate the reengineered business processes. The
two activities can be performed iteratively to provide mutual feedback. While business
process redesign can explicitly address the issues of customer satisfaction, the information
process reengineering can address the issues of information system efficiency and cost,
and take advantage of advancements in technology.
Workflow is a concept closely related to reengineering and automating business and
information processes in an organization. A workflow may describe business process tasks
at a conceptual level necessary for understanding, evaluating, and redesigning the busi-
ness process. On the other hand, workflows may capture information process tasks at a
level that describes the process requirements for information system functionality and
human skills. The distinction between these workflow perspectives is not always made,
and sometimes the term workflow is used to describe either, or both, of the business and
information systems perspectives.
Workflow management (WFM) is a technology supporting the reengineering of busi-
ness and information processes. It involves:
1. defining workflows, i.e., describing those aspects of a process that are relevant to con-
trolling and coordinating the execution of its tasks (and possibly the skills of individu-
als or information systems required to perform each task), and
2. providing for fast (re)design and (re)implementation of the processes as business
needs and information systems change
To effectively support WFM, organizations must evolve their existing computing envi-
ronments to a new distributed environment that:
is component-oriented, i.e., supports integration and interoperability among loosely-
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coupled components corresponding to heterogeneous, autonomous, and/or distributed
(HAD) legacy and new systems,
supports workflow applications corresponding to business or information process
implementations accessing multiple HAD systems,
ensures the correctness and reliability of applications in the presence of concurrency
and failures, and
supports the evolution, replacement, and addition of workflow applications and com-
ponent systems as processes are reengineered.
Many commercial systems have been introduced to support WFM. The genesis of
WFM software was probably in automating document-driven business processes [40].
Some of the early products were extensions to the document imaging and management
software [4]. Rosy estimates of fast expanding market size from less than $100 million in
1991 to about $2.5 billion in 1996 [27] drew significant interest of software companies,
and spawned a host of new products for WFM. Presently, commercial WFM systems for
office automation can support document management, imaging, application launching,
and/or human coordination, collaboration, and co-decision. Although many of these WFM
systems meet some of the requirements above, they allow only limited interoperability (in
terms of the types of HAD systems they can integrate and tasks they support), may not
ensure correctness or reliability of applications in the presence of concurrency and fail-
ures, and suffer from performance and scalability problems. Therefore, commercial WFM
systems currently cannot support enterprise-wide workflow applications effectively.
To satisfy these requirements, we believe that the following two key infrastructure
technologies must be combined with the capabilities commercial WFM systems already
provide:
distributed object management (computing)
customized transaction management
Distributed Object Management (DOM) [30,35,36] supports the interoperability and
integration of HAD systems and applications implementing business or information pro-
cesses. DOM allows WFM systems to cope with replacement, migration, and evolution of
HAD systems or changes in their functionality and data. In addition, DOM provides an
object model that facilitates managing complexity by the use of abstraction, inheritance,
and polymorphism. Other distributed computing approaches that currently offer a lower
level of interoperability than DOM may also be useful in providing interoperability for
WFM.
Customized transaction management (CTM) ensures the correctness and reliability of
applications implementing business or information processes, while permitting the func-
tionality each particular process requires (e.g., isolation, coordination, or collaboration
between tasks). In addition, CTM copes with changes in (i) the correctness and reliability
requirements of the process, and (ii) the correctness and reliability guarantees HAD sys-
tems provide.
In this paper, we discuss WFM technology from process specification to workflow
implementation. While the emphasis is more on the state-of-the-art in commercial WFM
systems, we also discuss the infrastructure technologies we believe can address the funda-
mental limitations found in today’s commercial WFM systems. In particular, we describe
only the technologies we believe can significantly improve the WFM technology and do
not attempt to comprehensively review all related research. Furthermore, we strive to give
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a balanced treatment to both process and data management issues. The paper by Krishna-
kumar and Sheth [24] provides a more detailed discussion of a workflow model, an “inter-
mediate” specification language, and a system architecture to support workflow
automation in an environment consisting of HAD systems.
The paper is organized as follows: In Section 2, we define WFM in greater detail. In
Section 3, we describe the principles of process modeling, and give examples. In Section
4, we discuss workflow specification and implementation as currently supported by com-
mercial WFM systems, as well as the limitations of WFM products. In Section 5, we dis-
cuss key infrastructure technologies for WFM and describe research issues and
corresponding work in progress. Specifically, we discuss the importance of DOM and
CTM technologies for the advancement of WFM technology. Our conclusions and some
perspective on future expectations are presented in Section 6.
2. Workflows and workflow management
There is little agreement as to what workflow is and which features a workflow man-
agement system must provide. Under the umbrella of the term “workflow”, which is often
used casually, people may be referring to a business process, specification of a process,
software that implements and automates a process, or software that simply supports the
coordination and collaboration of people that implement a process. Various concepts
attributed to the term workflow are illustrated in Figure 1.
For example, consider the following definitions of workflow from software vendors
which produce workflow products:
A representative of PeopleSoft Inc. states that “Workflow is the mechanism by which
you can implement business reengineering practices” [14].
Product literature from Action Technologies Inc. defines workflow as “work [that] is
recast as a series of people-based transactions” and states that “A series of workflows
form a business process” [14].
Product literature from Recognition Internal Inc. states that “simply defined, [work-
flow] is the process by which individual tasks come together to complete a transaction
- a clearly defined business process - within an enterprise” [3].
A Wang Laboratories representative states that “Workflow goes beyond routing [i.e.,
moving information among users or systems] by integrating information from a vari-
ety of sources” [14].
Other definitions of workflow distinguish workflow specification from workflow
Workflow
Business Process
specification/map
Business Process
reengineering Workflow automation
Workflow implementation
Workflow specification
Business Processes
automation
Business Process
Workflow management
Workflow management system
Figure 1. The “Workflow umbrella”
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implementation. For example, in [39] workflows are defined as activities involving the
coordinated execution of multiple tasks performed by different processing entities. A task
defines some work to be done and can be specified in a number of ways, including a tex-
tual description in a file or an electronic mail message, a form, or a computer program. A
processing entity that performs the tasks may be a person or a software system (e.g., a
mailer, an application program, a database management system). Specification of a work-
flow involves describing those aspects of its constituent tasks (and the processing entities
that execute them) that are relevant to controlling and coordinating their execution. It also
requires specification of the relationships (i.e., dependencies) among tasks and their exe-
cution requirements. These can be specified using a variety of software paradigms (e.g.,
rules, constraints, or programs).
The above workflow definitions do not clarify the relationship of the terms under the
workflow umbrella in Figure 1. In the following sections we provide definitions of these
concepts and give examples.
2.1. Workflows and workflow systems
We define a workflow as a collection of tasks organized to accomplish some business
process (e.g., processing purchase orders over the phone, provisioning telephone service,
processing insurance claims). A task can be performed by one or more software systems,
one or a team of humans, or a combination of these. Human tasks include interacting with
computers closely (e.g., providing input commands) or loosely (e.g., using computers only
to indicate task progress). Examples of tasks include updating a file or database, generat-
ing or mailing a bill, and laying a cable. In addition to a collection of tasks, a workflow
defines the order of task invocation or condition(s) under which tasks must be invoked,
task synchronization, and information flow (dataflow).
Figure 2 depicts three telecommunication workflows which require accesses to some
combination of shared databases.The New Service Provisioning workflow captures the
T2
New Service
T7
T5
T3
T4
T0
T6
T11
T10
T9
Customer
T17
T16
T15
T14
Service Change
Customer DB Billing DB Directory DB
Common
Resource
Databases
Provisioning
Billing
Provisioning
Switch
human task
T1
T13
computer task
T8
T18
T12
Facilities DB
Figure 2. Telecommunication workflows.
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process of telephone service provisioning for a new customer. The workflow takes place
when a telephone company customer requests telephone service installation.
Task T0 involves an operator collecting information from the customer. When suffi-
cient customer data are collected, task T1 is performed to (i) verify whether the informa-
tion provided by the customer is accurate and (ii) create a corresponding service order
record. On completion of T1, tasks T2, T3, and T4are initiated to perform three line provi-
sioning activities. The objective of a provisioning activity is construct a circuit from a cus-
tomer location to the appropriate telephone switch and allocate equipment to connect the
circuit. Only one of these provisioning tasks should be allowed to complete, as all will
result in a completed circuit, i.e., a set of lines and equipment that connects the customer
to a telephone network (this requirement is not depicted in Figure 2). T2 attempts to pro-
vide a connection by using existing facilities such as lines and slots in switches. If T2 suc-
ceeds, the cost of provisioning is minimal, i.e., the requested connection can be
established by allocating existing resources. However, a successful completion of this task
may not be possible if the facilities are not available. T3 and T4achieve the same objec-
tives as T2 but involve different paths for physical installations of new facilities. T5
requires manual work for facility installation. The human task T5 is initiated by providing
installation instructions to the engineers (e.g., via hand-held terminals) and is completed
when the human engineers provide the necessary work completion data. Task T6involves
changes in the telephone directory, while T7 updates the telephone switch to activate ser-
vice and then generates a bill. Finally, task T8involves a human operator who calls the
customer to inform him of the establishment of the requested service and verify that the
provided service meets the customer needs. In addition to the tasks involved, the workflow
defines the following task dependencies: (i) T1 starts after the completion of T0, (ii) T2,
T3, T4, and T6, can be performed concurrently after task T1 is completed, (iii) T5 must
start after the completion of T3 and T4, (iv) T7 is performed after the completion of T2, T5,
and T6, and (v) T8 starts after T7 completes.
The other workflows depicted in Figure 2 represent other telephone operations activi-
ties. Their tasks and the task sequencing have explanations similar to that of the New Ser-
vice Provisioning workflow.
A number of organizations have produced workflow management systems (WFMSs)
that provide the ability to specify, execute, report on, and dynamically control workflows
involving multiple humans and HAD systems [31]. The capabilities commercial WFMSs
currently offer are discussed in Section 4 and Appendix A.
2.2. Characterizing workflows
As yet, there is no commonly agreed way to characterize or categorize workflows or
WFMSs. Furthermore, most workflow characterizations neglect highly automated work-
flows accessing a large number of shared information systems. In Section 2.2.1, we
describe workflows and WFMSs as they are characterized by the trade press. In Section
2.2.2, we discuss another characterization of workflows that considers highly automated
workflows accessing shared information systems and emphasizes workflow implementa-
tion and automation requirements.
2.2.1 Trade press workflow characterization. The trade press often distinguishes
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between three kinds of workflow (this characterization was first given by McCready [27]):
ad hoc,administrative, and production. The dimensions along which these kinds of work-
flow are often described include:
repetitiveness and predictability of workflows and tasks
how the workflow is initiated and controlled, e.g., from human-controlled to auto-
mated
requirements for WFMS functionality
Ad hoc workflows perform office processes, such as product documentation or sales
proposals, where there is no set pattern for moving information among people [23,4]. Ad
hoc workflow tasks typically involve human coordination, collaboration, or co-decision
[41]. Thus, the ordering and coordination of tasks in an ad hoc workflow are not auto-
mated but are instead controlled by humans. Furthermore, the task ordering and coordina-
tion decisions are made while the workflow is performed. Ad hoc workflows typically
involve small teams of professionals and are intended to support short term activities
which require a rapid workflow solution, e.g., supporting the process of putting together
the program of a professional conference.
WFMSs that support ad hoc workflows must provide functionality for facilitating
human coordination, collaboration, and co-decision. Functionality for controlling task
ordering is typically not provided in such WFMSs. Users of an ad hoc workflow need to
access the WFMS to determine if work was completed. Also, ad hoc WFMSs are not mis-
sion critical, i.e., periodic failure of such workflows does not significantly interfere with
the overall business process. The infrastructure technology currently used by ad hoc
WFMSs ranges from “enhanced” electronic mail to group calendaring and conferencing
systems. Ad hoc WFMSs usually use a (proprietary) database to store shared information
(e.g., documents such as conference review forms or papers). WFMSs that support ad hoc
workflow are also called groupware.
Figure 3 illustrates a simplified ad hoc workflow involving the review process for con-
ference papers. The review process is to select reviewers, distribute the paper(s) to the
selected reviewers, have the reviewers perform the reviews and collaborate in producing a
joint review document, and finally forward it to the authors. This is an ad hoc workflow
because it involves: (i) negotiation for selecting the reviewers, and (ii) collaboration
between the reviewers for producing a joint review. Furthermore, subsequent paper
reviews may not be performed by the same reviewers.Thus, ad hoc workflows usually set
up procedures for performing and perform one-of-a-kind activities.
Administrative workflows involve repetitive, predictable processes with simple task
coordination rules, such as routing an expense report or travel request through an authori-
Distribute Review 2 Produce
Review 1
Review 3
Papers
Select
reviewers Review
Review
Review
...
joint review
request 1
request 2
request n
Forward
review
Figure 3. Ad hoc paper review workflow.
126
zation process. The ordering and coordination of tasks in administrative workflows can be
automated. WFMS that support administrative workflow handle simple information rout-
ing and document approval functions, such as those found in travel planning and purchase
requests. Administrative workflows do not encompass a complex information process and
do not require accesses to multiple information system used for supporting production
and/or customer services. Administrative WFMS are generally non-mission critical. The
infrastructure technology they currently use is typically based on electronic mail.
Consider again the paper review process. However, this time assume that the reviewers
are known in advance (e.g., the same reviewers are used for all paper reviews). Further-
more, suppose that the reviewers do not collaborate in producing a joint review. Instead,
they produce individual reviews that are considered by the editor (e.g., program chair)
who makes the final decision. Under these assumptions the paper review workflow
becomes an administrative workflow such as depicted in Figure 4.
In an administrative workflow users are actively prompted to perform their tasks.
Whereas reviewers using an ad hoc workflow needed to access the WFMS to determine if
work was completed, reviewers using an administrative WFMS may receive email with
review instructions along with the paper to be reviewed and a reviewer’s comments form.
When the form is completed, it is automatically routed to the program committee chair-
person who is alerted when all of the reviews are completed.
Production workflows involve repetitive and predictable business processes, such as
loan applications or insurance claims. Unlike administrative workflow, production work-
flows typically encompass a complex information process involving access to multiple
information systems. The ordering and coordination of tasks in such workflows can be
automated. However, automation of production workflows is complicated due to: (i) infor-
mation process complexity, and (ii) accesses to multiple information systems to perform
work and retrieve data for making decisions (administrative workflows rely on humans for
Distribute Review 2 Combine
Review 1
Review 3
Papers Forward
review
reviews
Figure 4. Administrative paper review workflow.
Index Assess Claim Adjudicate
Make
Claim Form Claim
Scan
Claim Form
Payment
Reject
OK
Claim Image DB Claims DB Eligibility DB
Finance DB
OK
reject
Claims expert claim
system
Figure 5. “Health Claims Process” workflow.
127
most of the decisions and work performed).
WFMSs that support production workflow must provide facilities to define task depen-
dencies, and control task execution with little or no human intervention. Production
WFMSs are often mission critical and must deal with the integration and interoperability
of HAD information systems.
Consider the simplified health claims process workflow depicted in Figure 5. In the
health claims workflow, a claim form is first manually scanned and stored into an object
database. Then the claim is manually indexed in a relational database. This information is
subsequently analyzed by an automated “Assess Claim” task. The task is performed by an
expert system which uses an eligibility database to determine if payment should be made.
If the claim is rejected, a claim representative discusses the claim with the customer and
either agrees to make some payment, or to reject the claim. If payment is made, the “make
payment” task accesses the finance database and records the payment. The significant dif-
ferences between this production workflow and either the ad hoc or administrative work-
flow are: (i) the interaction of information systems with the business process, and (ii) the
use of automated (non-human) task performers.
The relationship of ad hoc, administrative, and production workflow is illustrated in
Figure 6 [23] using task structure versus complexity.
Workflow with little structure may involve a linear path of tasks to be followed; highly
structured workflow may involve a graph-like organization of tasks where some tasks may
be executed in parallel or multiple tasks must complete before others can start. Complex-
ity can be determined by the kinds of coordination/collaboration rules or constraints
applied to task execution. For example, one aspect of complexity could be a requirement
that a task begins execution only after a set of events has occurred. Complexity is also
reflected by the kinds of HAD systems that must be integrated to produce a task imple-
mentation, e.g., office applications, DBMSs, or legacy information systems.
Other characterizations of workflows have recently appeared in the trade press [1,14].
[1] divides workflows into ad hoc workgroup support, task automation, document flow,
and process automation. [14] divides workflows into three categories: mail-centric, docu-
ment-centric and process-centric. These characterizations do not separate workflow
semantics from the commercial WFMS that support them, and the infrastructure technol-
ogy they are currently using. Furthermore, trade press workflow characterizations typi-
cally do not distinguish between production workflows accessing a small number of
homogeneous information systems and highly automated workflows accessing many
Complex
Simple
Low High
Task Structure
Task Complexity
Insurance Claims
Loan Applications
Product Documentation
Sales Proposals
Press Releases
Expenses
Travel Requests, Purchase Requests
Messages
Production
Ad Hoc
Administrative
Telecommunications & controlMilitary command
Figure 6. Trade press characterization of workflow.
128
shared HAD information systems. For example, workflows in the domains of military
command and control, or telecommunications belong in the latter category. Such work-
flows are not discussed or characterized by the trade press. Using the complexity versus
structure framework in Figure 6, these workflows have requirements with greater structure
and complexity than those found in production workflows. Since workflows in domains
such as military command and control or telecommunications involve HAD systems with
greater heterogeneity (e.g., controlling telecommunications switch hardware in telecom-
munications) and greater demands for correct and reliable execution (e.g., military appli-
cations on whose data integrity lives depend), their implementation and automation
requirements are greater than those in production workflows. As a result we now charac-
terize workflows according to their implementation and automation requirements.
2.2.2 Our characterization of workflow. We characterize workflow along a continuum
from human-oriented to system-oriented as depicted in Figure 7. On the one extreme,
human-oriented workflow involves humans collaborating in performing tasks and coordi-
nating tasks. The requirements for WFMSs in this environment are to support the coordi-
nation and collaboration of humans and to improve human throughput. Humans, however,
must ensure the consistency of documents and workflow results.
On the other extreme, system-oriented workflow involves computer systems that per-
form computation-intensive operations and specialized software tasks. In addition to being
highly automated, system-oriented workflows access HAD information systems. While
human-oriented workflow implementations often control and coordinate1 human tasks,
system-oriented workflow implementations control and coordinate software tasks (typi-
cally with little or no human intervention). Consequently, system-oriented workflow
implementations must include software for various concurrency control and recovery
techniques to ensure consistency and reliability. This is not required and cannot be pro-
vided by WFMS that support human-oriented workflows. Human-oriented workflows
have process semantics (e.g., capture where to route a document) but have no real knowl-
edge of the (semantics of) the information being processed. Therefore, in human-oriented
workflows the WFMS is there to assist people and the WFMS cannot be made responsible
for maintaining data consistency, since it has no information semantics. On the other hand,
system-oriented workflows have more knowledge of information semantics (e.g., built-
into the various applications involved and the information systems that synchronize appli-
cation access to shared databases). Hence the WFMS can be given (and must be given)
more responsibility for maintaining information consistency.
In human-oriented workflow, the main issues to address include:
human-computer interaction
matching human skills to task requirements
Human-oriented System-oriented
CSCW
Commercial Workflow
Transactional workflows
Commercial Transaction
Management Systems Processing Systems
Figure 7. Characterizing workflow.
129
changing office culture, i.e., how people need or prefer to work
In systems-oriented workflow, the issues to address include:
matching business process requirements to functionality and data provided by existing
information systems and/or their applications
interoperability among HAD systems
finding appropriate software tasks to perform workflow tasks
determining new software required to automate business processes
ensuring correct and reliable system execution
Issues such as exception handling, user overrides, prioritization, and deadline may
appear in different forms in both types of system, and need to be addressed. Also depicted
in Figure 7 are segments indicating a range of workflow characteristics and issues that are
addressed by (i) the field of computer supported cooperative work (CSCW), (ii) commer-
cial WFMSs, and (iii) commercial transaction processing (TP) systems (e.g., distributed
DBMSs, TP monitors). CSCW overlaps with WFM where workflows involve predomi-
nantly human tasks. Commercial TP systems overlap with WFM when workflow applica-
tions are submitted as DBMS or TP monitor transactions.
Transactional workflows involve coordinated execution of multiple tasks that (i) may
involve humans, (ii) require access to HAD systems, and (iii) support selective use of
transactional properties (e.g., atomicity, consistency, isolation, and/or durability) for indi-
vidual tasks or entire workflows. Selective use of transactional properties is required to
allow the specialized functionality required by each workflow (e.g., allow task collabora-
tion and support complex workflow structures). Since the traditional transactions DBMS
and TP monitors provide do not permit selective use of transactional properties to allow
specialized functionality (e.g., DBMS-provided transactions enforce isolation and this
does not permit the cooperation of tasks or workflows), extending or relaxing the transac-
tion models DBMS and TP monitors provide is needed to support workflow functionality
requirements. WFMSs currently do not address key aspects of system-oriented workflow
such as HAD systems and WFMS interoperability and integration, and ensuring correct
and reliable workflow execution in the presence of concurrency and failures. Transac-
tional workflows and the technology needed to support these are discussed further in Sec-
tion 5.2.
2.3. Workflow management
In the rest of this paper we use the generic term process to refer to a business process, a
Process Workflow
Specification Workflow
Implementation
methodology methodology
methodology
workflow
application
=
executable - interoperability
- integration
- correctness
- reliability
- workflow model
- specification language - rule definitions
- task programs
- WFMS
Figure 8. Workflow management issues.
130
business process and its corresponding information process, or an information process.
Workflow management involves everything from modeling processes up to synchronizing
the activities of information systems and humans that perform the processes. In particular,
management of a workflow includes the following (as illustrated in Figure 8):
1. process modeling and workflow specification: requires workflow models and method-
ologies for capturing a process as a workflow specification,
2. process reengineering: requires methodologies for optimizing the process, and
3. workflow implementation and automation: requires methodologies/technology for
using information systems, and human performers to implement, schedule, execute,
and control the workflow tasks as described by the workflow specification.
The following paragraphs discuss each of these workflow management issues.
Modeling a process. Before we capture a process we first need to understand it. This usu-
ally involves interviewing people with expert knowledge about the process. Interview
methodologies such as those used for expert system design are appropriate for conducting
such interviews. When enough knowledge about the process is obtained, workflow speci-
fication is performed to capture the process.
GTE Telephone Operations is performing a large process reengineering effort [11].
GTE Telephone Operations formed reengineering teams (20-25 employees) to capture
existing business processes and redesign its core business processes. Teams documented
existing business processes by conducting 1000 interviews and 10,000 observations, and
produced corresponding workflow specifications using a workflow specification tool.
In addition to understanding a business process, modeling the process involves work-
flow specification. A workflow specification captures a process abstraction. The process
abstraction level in a workflow specification depends on the intended use of the workflow
specification. For example, a workflow specification may describe a process at the highest
conceptual level necessary for understanding, evaluating, and redesigning the process. On
the other hand, another workflow specification may describe the same process at a lower-
level of detail required for performing workflow implementation.
Performing workflow specification requires a workflow model. A workflow model typi-
cally includes a set of concepts that are useful to describe processes, their tasks, the depen-
dencies among tasks, and the required roles (i.e., skills of the individuals or information
systems) that can perform the specified tasks. Workflow models are discussed further in
Section 3.
Workflow specification is typically performed using a workflow specification language.
Workflow specification languages in commercial WFMS use rules, constraints, and/or
graphical constructs to describe the ordering and synchronization of tasks in a workflow,
and task attributes to describe the tasks and the roles to perform them. For example, a
graphical workflow specification may be similar to the illustration in Figure 2 (possibly
without including the common resource databases unless they indicate the roles of the
information systems and the humans required to implement the specified tasks). An exam-
ple rule in a rule-based specification of the New Service Provisioning process in Figure 2
might be: On T1 completion Do start T2, T3, T4, T6. This rule captures the fact that in tasks
T2, T3, T4,and T6must be executed after the completion of task T1.
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Reengineering a process. The objective of re-engineering methodologies is to optimize
business processes. Process optimization strategies depend on the reengineering objec-
tives (e.g., increasing customer satisfaction, reducing the cost of doing business, introduc-
ing new products or services). Reengineering methodologies are currently an art.
Workflow specification provides a high-level description of a process that facilitates high-
level reasoning about business process efficiency.
An effort undertaken at NYNEX to reengineer the process for provisioning of requests
for T-1 lines is reported in [34]. The GTE Telephone Operations reengineering effort and
the RAPID methodology used for improving customer service and reduce the information
system costs are described in [11].
Implementing and automating a workflow. Implementation deals with the issues associ-
ated with realizing a workflow using computers, software, information systems, and/or
WFMSs. Workflow automation deals with scheduling and controlling workflow execu-
tion.
No workflow implementation or automation is required when the only reason for work-
flow specification is to capture business processes and reason about their efficiency. Other-
wise, workflow specifications are used to implement and automate workflows. In
particular, workflow specification and implementation and can be loosely coupled (e.g.,
workflow specifications are implemented by software engineers) or tightly coupled (e.g.,
workflow specifications are provided as direct input to a WFMS that either generates code
or interprets specifications for controlling workflow execution).
Many commercial workflow management systems take the tightly coupled approach
from workflow specification to workflow implementation. The implication is that the
dividing line between what is the workflow specification and workflow implementation is
not always sharp.
Automated workflow implementations are typically distributed applications that access
HAD systems. Like any other distributed HAD system application, a WFMS has to deal
with application integration, interoperability, and implementation correctness and reliabil-
ity. Limitations of WFMSs in dealing with these issues, and infrastructure technologies
that can be used to address these limitations, are discussed in Section 5.
3. Process modeling and workflow specification
Process modeling involves capturing a process in a workflow specification. In this sec-
tion, we discuss workflow models and corresponding process modeling methodologies.
3.1. Methodologies for process modeling
There are two basic categories of process modeling methodologies: communication-
based and activity-based [29].
The communication-based methodologies stem from Winograd/Flores “Conversation
for Action Model” [42]. This methodology assumes that the objective of business process
re-engineering is to improve customer satisfaction. It reduces every action in a workflow
to four phases based on communication between a customer and a performer (illustrated
in Figure 9):
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1. preparation - a customer requests an action to be performed or a performer offers to do
some action
2. negotiation - both customer and performer agree on the action to be performed and
define the terms of satisfaction
3. performance - the action is performed according to the terms established
4. acceptance - the customer reports satisfaction (or dissatisfaction) with the action
Each workflow loop between a customer and performer can be joined with other work-
flow loops to complete a business process. The performer in one workflow loop can be a
customer in another workflow loop. The resulting business process reveals the social net-
work in which a group of people, filling various roles, fulfill a business process.
The example in Figure 10 illustrates a business process for procuring materials. The
main workflow loop (procure materials) requires several secondary workflow loops during
the performance phase (verify status, get bids, place order). In particular, an investigator
requests services from the procurement office for materials. In the performance of pro-
curement, the procurement office instructs the accounts office to verify the account status
of the purchaser. The procurement office then contacts vendors for bids, and finally selects
a vendor to place an order. The workflow is completed (i.e., the main loop is closed) when
the procurement office reports to the investigator that the materials have been procured.
Note that the performer in the main loop is the customer in the secondary loops. Also note
that workflow specifications using this methodology do not indicate which activities can
occur in parallel or if there are conditional or alternative actions.Since this methodology
assumes that the objective of business process re-engineering is to improve customer sat-
isfaction, the emphasis is on the customer. However, there are business processes where
the customer emphasis may be superficial, e.g., if the objectives are to minimize informa-
tion system cost or reduce waste of material in a process. Therefore, this methodology is
not appropriate for modeling business processes with objectives other than customer satis-
faction. Another limitation is that this methodology by itself does not support the develop-
ment of workflow implementations for specifications.
The “ActionWorkflow Analyst” tool [33,3] from Action Technologies is based on the
Winograd/Flores model, as is the “Business Transformation Management” tool from Busi-
ness Transaction Design [29].
preparation negotiation
performance
acceptance
Customer Performer
Workflow Loop
Figure 9. Conversation for Action Model.
Procure Materials Verify Status
Get Bids
Place Order
accounts
office
vendors
vendor
investigator procurement
office
Figure 10. Workflow for procuring materials.
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Activity-based methodologies focus on modeling the work instead of modelling the
commitments among humans. For example, consider the workflow depicted in Figure 11
where the process “procure materials” is composed of several tasks. The arrows indicate
the sequential nature of this process map. Note that “procure materials” may be a task in
yet another workflow, and that tasks may nest arbitrarily deeply. Unlike communication-
based methodologies, activity-based methodologies do not capture process objectives
such as customer satisfaction.
Many commercial WFMS provide activity-based workflow models. For example, in
the workflow model supported by InConcert [31], workflows (referred to as jobs) consist
of tasks. Each task may be comprised from subtasks. Each task has dependencies on other
tasks at the same level and has an assigned role which is the proxy for a human or a pro-
gram that performs the task. GTE’s RAPID methodology [11] is also activity-based.
RAPID provides two workflow models: a high-level model for performing conceptual
business process analysis and a lower-level model for describing the corresponding infor-
mation process. In the high-level workflow model, workflows (referred as process maps)
contain tasks (referred as steps) necessary to perform a particular business process. These
steps can be partially or totally ordered as necessary to indicate alternatives or parallel
execution of business process steps.
The communication-based and activity-based workflow models can be combined when
process re-engineering objectives are compatible with both models (e.g., satisfy the cus-
tomer by minimizing workflow tasks and human roles). For example, the workflow model
used for the telecommunications workflows in Figure 2 can be viewed as both activity-
based and communication-based.
Object-oriented methodologies, such as those proposed in Rumbaugh et al. [38] and
Jacobson [22] may be useful in defining workflow specifications (and deriving implemen-
tations). For example, Jacobson [22] describes how to (i) identify objects that correspond
to “actors” (i.e., workflow roles), (ii) identify the dependencies between those objects, (iii)
use object techniques such as inheritance to organize object specifications, and (iv)
describe “use cases” which are essentially a sequence of tasks needed to complete some
business process. Use cases may also include “alternative courses” which describe how to
handle exceptional conditions. However, object orientation provides no explicit support
(e.g., workflow model) for process modeling. The object designer typically must define
workflow model-specific objects from scratch. This problem can be addressed if work-
flow-model-specific types and classes (e.g., customer, employee, document, computer sys-
tem, workflow, step, etc.) are defined to support business process modeling directly.
Some commercial business process modeling tools use object oriented concepts and
techniques for representing, as well as implementing processes. For example, InConcert
[31] and ObjectFlow [21] combine object-orientation with the activity-based methodol-
ogy.
Procure Materials
Verify Status Get Bids Place Order
task nesting
Figure 11. Workflow for procuring materials.
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3.2. Technology status and research issues
Many commercial WFMSs, including those discussed in this section, support workflow
definition for process modeling. However, to facilitate the use of workflow across vendor
products, a standard representation for workflow specification is necessary. A standards
body called the Work Flow Management Coalition was formed in 1993 to address the lack
of standards for WFMSs. Their objectives include standardizing workflow model specifi-
cations to allow the interoperability of workflow specifications supported by different
WFMSs. Interoperability of workflow specifications is an open research issue.
Another problem with current commercial technology is that the workflow models and
process modeling methodologies do not explicitly support the specification of what it
means for a workflow to be correct, e.g., what tasks must complete for the workflow to be
considered successful. For example, in a telecommunications service provisioning
domain, a workflow may be considered successful if a bill is produced, even if the direc-
tory is not updated to indicate customer changes. Research in the area of transaction man-
agement can provide modeling constructs for augmenting existing workflow models to
address correctness and reliability.
Finally, process modeling methodologies have not addressed workflow implementation
involving legacy information systems. For organizations that rely on legacy information
systems, workflow specification for performing workflow implementation requires map-
ping workflow specifications to legacy system functionality and data. If this is not done,
process reengineering may produce workflow specifications that cannot be supported by
the legacy information systems.
4. Workflow implementation and automation
As we briefly discussed in Section 2.3, many commercial WFMSs have taken the
tightly coupled approach from workflow specification to workflow implementation, i.e.,
they are using workflow specifications to produce corresponding workflow implementa-
tions. This approach is a powerful paradigm for process implementation, since it elimi-
nates the dividing line between workflow specification and implementation. In this section
we focus on the tightly coupled approach and discuss the capabilities and limitations of
commercial WFMSs.
In particular, in Section 4.1 we describe the capabilities currently supported by com-
mercial WFMSs (a partial list of WFMS vendors and products can be found in Appendix
A). In Section 4.2, we discuss commercial WFMS limitations, particularly in the areas of
integration with HAD information systems and support for workflow correctness and reli-
ability. In Section 5, we discuss infrastructure technologies that can complement the capa-
bilities of commercial WFMS to address these limitations.
4.1. Commercial workflow management systems
In this section we discuss the features and capabilities currently supported by commer-
cial WFMSs with respect to workflow model, specification language, tools for testing/
analysis and monitoring, system architectures and interoperability, implementation sup-
port, and correctness and reliability.
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Workflow model. WFMSs provide both activity-based and communication-based work-
flow models for specifying workflows. For example, InConcert, Staffware, and FloWare
use activity-based workflow models, while ActionWorkflow uses a communication-based
model.
The workflow models most WFMSs support are activity-based, and consist of elements
similar to the following:
workflows: a partial or total ordering of a set of tasks
tasks: a partial or total order of operations, descriptions for human actions, or other
tasks
manipulated objects: documents, data records, images, phones, fax machines, printers,
etc.
roles: a placeholder for a human skill or an information system service required to per-
form a particular task
agents: humans or information systems that fill roles, perform tasks, and interact dur-
ing workflow execution
To provide different levels of abstraction, WFMSs typically support the nesting of
tasks. For example, the workflow that provides a new customer with telephone service
involves tasks of acquiring customer information, allocating facilities, and setting up cus-
tomer billing. The task for allocating facilities may in turn be comprised of several line
provisioning sub-tasks that explore different line provisioning alternatives (e.g, use of
existing facilities or installation of new facilities). Each level of abstraction provides a
view to the workflow specification. Higher levels of abstractions help management follow
or control a business process. The lower levels of abstraction are required to capture
exactly what is required to implement a workflow.
The definition of roles in a workflow is particularly beneficial when a task can be per-
formed by more than one agent. The mapping of agents to roles (role/user administration
in Appendix B) helps to manage change in the work force and the computing environ-
ment. In addition, it can facilitate dynamic load balancing. For example, if the role is ‘Pur-
chaseOrderApprover’, a purchasing department may have several users (human agents)
who can fill this role. If the workload on one PurchaseOrderApprover is high, the system
can automatically pass a request to another PurchaseOrderApprover.
Specification language. All WFMSs of which we are aware provide graphical work-
flow specification languages. In addition, many WFMSs provide rule-based or constrained
workflow specification languages. These languages are higher-level languages than stan-
dard programming languages such as C and C++. They support the specification of the
following:
task structure (control flow) and information exchange between tasks (dataflow) in a
workflow, e.g., specifying that tasks can be executed in parallel, or that a task needs to
wait for data from other tasks)
exception handling, e.g., specifying what actions are necessary if a task fails or a
workflow cannot be completed
task duration, e.g., specifying initiation and completion time of a task
priority attributes, e.g., specifying priorities for task scheduling
In rule- or constraint-based workflow specification languages, the workflow structure
and dataflow are typically specified by defining routing rules or constraints. Routing is
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often classified as conditional,rule-based, or parallel. Conditional routing involves
scheduling a task based on data values. For example, “if item.cost > 1000, then contact
Manager.” Rule-based routing is more powerful than conditional routing and can involve
arbitrarily complex rules stated in a rule-based language. Parallel routing allows one task
to branch into multiple others that can execute in parallel. A few languages also explicitly
support task rendezvous.
Graphical user interfaces (GUIs) are provided for both graphical workflow specifica-
tion and graphical task specification. Graphical workflow specification languages support
the iconic representation of workflow tasks and the ability to sequence those tasks graphi-
cally by connecting arrows and decision icons among workflow tasks. Many WFMSs use
graphical specification to automatically generate code or set up rules for a workflow
implementation and execution.
GUIs for task specification support the creation of programming interfaces for tasks
involving programs, and graphical interfaces for tasks involving humans.
Testing, analysis, and monitoring tools. Workflow testing tools simulate a workflow by
allowing input of sample data and triggering events such as task completion, deadline
expiration, and exceptions. Simulation is needed to uncover logic errors and get estimates
of workflow completion times.
Workflow analysis tools are needed to predict possible bottlenecks in a workflow by
analyzing the workflow specification. The analysis is done by taking into account work-
flow execution or simulation statistics. For example, analysis tools can gather statistics on
workflow performance and suggest alterations to the workflow specification to improve
efficiency. Some products supply simple testing and/or analysis tools, but typically they
are inadequate.
Once a workflow is implemented, we need to monitor its progress, e.g., for checking
the status of a workflow, or determining bottlenecks. WFMSs provide GUIs that can
present different views of workflow execution, e.g., they illustrate which task or tasks are
currently active, by whom they are performed, the task priorities, task deadlines, task
durations, and task dependencies. Managers can use such monitoring tools to access work-
flow statistics such as task completion times, workloads, and user performance, as well as
to generate reports and provide periodic summary of workflow executions.
Systems architecture and interoperability. Some commercial WFMSs have open client-
server architectures and complete application programming interfaces (APIs) (i.e., such
that everything that can be done through the user interface can also be done via an API).
WFMSs support exchange of information among users or systems via email or a shared
(usually WFMS vendor proprietary) database (in Appendix B we use the term transport to
refer to the way information exchange is implemented). Email supports human notifica-
tion and databases are used to maintain shared documents. Administrative WFMSs are
often based on email. Ad hoc and production WFMSs typically store information in a
shared database. Many WFMSs provide a combination of these.
Many WFMSs support limited interoperability among some office applications that
manipulate documents. For example, Lotus Notes uses Microsoft’s OLE which provides a
protocol for document interoperability.
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Implementation support. Although GUIs and APIs contribute greatly to implementa-
tion support, there are other capabilities (i.e., with or without GUIs) that support ease of
implementation, maintenance, and use. These include:
dynamic modification of workflow - the ability to change task sequencing or introduce
new tasks into an executing workflow
event signaling and notification - the ability for programmers to raise events in one
task and have another task “notice” that event and take action on it. This allows a loose
coupling among tasks without embedding rules in task code. For example, a WFMS
may support deadline management which notifies users when active tasks approach
their deadline
user administration - associate users to roles and support the management of these
associations
Dynamic Workflow Modification, Event Signaling (Event-Action Triggers), and Role/
User Administration are popular WFMS features. They are provided by all WFMSs com-
pared in Appendix B.
Correctness and reliability. When multiple objects (e.g., databases, files, documents,
devices) are accessed by a workflow execution, data consistency problems can arise either
from concurrency, application failures, system failures, or network failures. These intro-
duce the need for concurrency control,recovery, and transaction coordination. Most com-
mercial WFMSs provide limited capabilities to deal with these problems, with a few
notable exceptions such as FlowMark which keeps a log of performed actions and work-
flow states and supports automatic restart after failures [25].
In many situations concurrency control is essential when two or more users (or com-
puter systems) can access the same data object. However, commercial WFMSs take
widely different approaches to concurrency control, depending on perceived workflow
requirements. For example, some WFMSs (e.g., XAIT’s InConcert) support a form of
check-in and check-out on data items such that users can “lock” data to preclude concur-
rent access by other users. Check-in and check-out is a primitive way to handle concur-
rency when compared to how DBMSs support concurrency, and may not ensure workflow
consistency.
Other WFMSs (e.g., Lotus Notes) allow multiple users to retrieve the same data object
concurrently. If each user decides to update that data object, new versions of the data item
are created to be reconciled (merged) by human intervention. The rationale for this
approach is the assumption that data object updates are rare. Thus, consistency can be han-
dled by humans who review the data object versions and decide which one they want to
keep. If this assumption is not met, this approach has potentially serious ramifications.
Consider an example where multiple users retrieve hundreds if not thousands of data
objects from a WFMS-controlled database, perform some automated procedure on them,
and return those changes to the database. This may result in thousands of object versions
all requiring human intervention to merge. Clearly, this poses a problem not only because
of the time required to review these objects, but also the potential for conflicting informa-
tion which cannot be correctly merged.
Still other WFMSs (e.g., Sietec’s Staffware) use a pass-by-reference/pass-by-value
approach for concurrency control. Data items (e.g., documents) that can be shared among
multiple users are passed by reference, i.e., users access a centrally stored data item using
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a handle (pointer), possibly concurrently. This approach requires some form of concur-
rency control to provide an adequate level of non-interference among users.
Workflow recovery involves (i) how to undo completed or partially completed tasks
that cannot be completed due to a failure, and (ii) how to undo a cancelled workflow. For
example, consider a telephone service provisioning workflow that, among other things,
updates a customer database and billing database, and allocates facilities for the customer.
If a customer requests service and later cancels service before installation is completed,
two options are possible: (i) allow the workflow to complete and execute a separate work-
flow that cancels service, or (ii) discontinue the workflow and undo completed tasks. The
first option is simpler, since it does not involve undoing tasks. However: (i) compute
power is wasted to finish processing a workflow known to be useless, (ii) human effort is
wasted if facilities must be installed to support service that will soon be disconnected, (iii)
a second workflow must be executed taking additional resources, and (iv) allocated facili-
ties cannot be used to support the needs of other workflows.
The second option, i.e., stopping the workflow as soon as it is known to be useless,
avoids these concerns. However, the ability to stop, or abort, a workflow in the middle of
its execution requires additional support from the WFMS. In particular, the WFMS must
maintain the state of each task, and use these to reach a consistent state from which it can
undo the effects of failed workflows.
Most commercial WFMSs rely on workflow designers for providing workflow specifi-
cation to deal with reliability problems. For example, InConcert deals with workflow and
task failures by allowing dynamic modification of workflows to specify tasks that perform
compensation or alternative actions. As tasks and workflows become more automated,
however, the speed at which business processes are performed and the volume of data
being affected makes human-controlled recovery impractical. No commercial WFMSs we
are aware of offers significant support for workflow recovery.
4.2. Limitations of workflow management systems
Despite their many features, WFMSs have a number of significant limitations. These
include:
lack of interoperability among WFMSs
lack of support for interoperability among HAD systems or among WFMS and HAD
systems
inadequate performance for some business processes
lack of support for correctness and reliability
weak tool support for analysis, testing, and debugging workflows
Lack of interoperability among WFMSs. This is directly attributable to the lack of stan-
dards for WFMSs. As discussed in Section 3.2, the Work Flow Management Coalition, a
standards body, was formed in 1993 to promote interoperability among WFMSs. Their
standards address the areas of (i) APIs for consistent access to WFMS services/functions,
(ii) specifications for formats and protocols between WFMSs themselves, and between
WFMSs and applications, and (iii) workflow model interchange specifications to allow the
interchange of workflow specification among multiple WFMSs. Most WFMS vendors are
members of this coalition.
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Lack of support for HAD system interoperability and integration. For workflows that
access HAD information systems, full interoperability among HAD systems, WFMSs, and
workflow implementations is important for the following reasons:
1. it simplifies workflow implementation, i.e., interoperability allows WFMSs to access
HAD systems without requiring any HAD system-specific code,
2. it allows fast workflow implementation, i.e., workflow implementations that do not
include HAD system-specific code can be developed faster that those that involve pro-
gramming, and
3. it requires minimal workflow re-implementation to cope with changes in HAD system
functionality, i.e., it requires no code changes in workflow implementations except re-
specification of HAD system interfaces.
Some commercial WFMSs support limited interoperability among office applications
meeting specific platform, interface, or operating system requirements. For example, some
WFMSs (e.g., Lotus Notes) use Microsoft’s OLE as a protocol for document interopera-
bility. However, further interoperability requires WFMSs to take advantage of technology
that complies with industry standards for interoperability, such as those developed by the
Object Management Group (OMG).
Inadequate performance. Commercial WFMSs typically support no more than a few
hundred workflows a day. Some processes require handling a larger number of workflows;
perhaps a number comparable to the number of transactions TP systems are capable of
handling. For example, telecommunications companies currently need to process ten thou-
sand service provisioning workflows a day, including a few thousand service provisioning
workflows per hour at peak hours. Commercial WFMSs are currently not capable of han-
dling such workloads.
Lack of support for correctness and reliability in the presence of concurrency and fail-
ures. Workflow execution (like any execution of applications that access shared resources)
must address the following three correctness concerns: the consistency of individual tasks,
the consistency of individual workflows (i.e., the consistency of concurrent executions of
tasks that belong to the same workflow), and the consistency of concurrent executions of
tasks that belong to different workflows. Usually, the person who implements a task is
responsible for ensuring that the task produces correct results if it is executed alone. It is
also reasonable to assume that if correct tasks are executed one after the other in an order
allowed by workflow specification rules, such an execution of a workflow preserves con-
sistency by design. However, if tasks are executed concurrently with tasks of the same or
other workflows, and the tasks share resources, their individual operations may interleave
in such a way as to produce incorrect results. These are well-understood issues in database
transaction processing.
The workflow reliability problem involves restoring consistency when a workflow ter-
minates abnormally (e.g., due to a system failure, lack of available resources, or inability
to achieve objectives). Completed tasks of a partially completed workflow may be undone
or compensated. Alternatively, incomplete tasks of a partially completed workflow may
need to be redone or contingency tasks need to be performed. Clearly, it is important to
know which tasks have been completed, which are still active, which have not begun, and
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which tasks need to be undone or redone to restore consistency.
To deal with these problems, WFMSs rely on (i) workflow designers for providing
specifications that include compensating tasks and actions, and (ii) task/workflow pro-
grammers for providing code for concurrency control and keeping logs. This solution is
unrealistic, as most workflow designers/programmers are not skilled in concurrency con-
trol and recovery technology. Moreover, software to implement concurrency control and
recovery mechanisms is complex. Finally, testing and debugging software with hard-
coded correctness and reliability functions is time-consuming and error prone.
Weak tool support for analysis, testing, and debugging of workflow specifications and
implementations. As discussed in Section 4.1, such tools are needed to estimate workflow
specification and implementation efficiency, simulate workflow execution, and determine
the source of workflow specification and implementation problems. The sophistication of
such tools directly impacts rapid prototyping, and ease of workflow specification and
implementation.
Overall evaluation. Some limitations of current WFMSs can be attributed to their
youth, e.g., lack of standards and tools for conceptual modeling, testing, debugging, and
analysis. Other limitations, however, are fundamental to the design of the WFMSs we
have investigated, e.g., lack of support for interoperability, as well as correctness and reli-
ability support. In the following section we discuss technologies that can be integrated
with workflow management to address these limitations.
5. Key infrastructure technologies for workflow management
Efficient and reliable support for workflow implementation and execution requires a
distributed computing environment that:
supports integration and interoperability among loosely-coupled HAD legacy and new
systems,
supports workflow applications that require access to multiple HAD systems,
ensures correctness and reliability of workflow applications in the presence of concur-
rency and failures, and
supports evolution, replacement, and addition of workflow applications and systems as
business processes change.
Commercial WFMS satisfy some of these requirements. In particular, commercial
WFMS facilitate the process of specifying and implementing workflows by: (i) providing
a constrained environment using a limited set of concepts to specify and implement work-
flows, and (ii) keeping workflow structure (i.e., the rules for sequencing of tasks) sepa-
rated from the task implementation code. The latter allows changes in workflow structure
without modifying the programs that implement the workflow tasks. Thus, WFMSs sup-
port efficient (re)design and (re)implementation of workflows as business needs change.
In addition, WFMSs cope with changes in HAD systems and the tasks they support by re-
implementing affected workflows.
To address the remaining requirements, two key infrastructure technologies, Distrib-
uted Object management (DOM) and Customized Transaction Management (CTM), can
be combined with the WFMS capabilities that commercial WFMS already provide. DOM,
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as partly exemplified by software complying with the OMG’s Common Object Request
Broker Architecture (CORBA) [35,36], is one of several fast maturing distributed comput-
ing technologies and standards that are useful in providing HAD system interoperability.
We believe that DOM is particularly useful for supporting workflow management for the
following reasons:
it supports the interoperability of HAD systems and applications implementing work-
flows,
it copes with changes that result from replacement, migration and evolution of HAD
systems, and
it provides an object model that helps manage complexity and provides more transpar-
ency than other distributed computing technologies exemplified by DCE [BGHM93]
(other infrastructure alternatives such as DCE may be useful in the short term until
DOM technology becomes more mature).
DOM is discussed further in Section 5.1
CTM complements DOM by:
providing the correctness and reliability each workflow requires,
dealing with differences in HAD system-provided correctness and reliability guaran-
tees, and
coping with changes in application correctness and reliability requirements.
CTM is described in Section 5.2.
5.1. Distributed object management
DOM [30,35,36,28] supports the interoperability and integration of component HAD
systems by: (i) representing their data and functionality as objects, and (ii) allowing client
applications (such as workflow implementation) to invoke behavior on server objects typ-
ically without regard to an object's location, data representation, or access language. In
addition, DOM provides an object model that facilitates managing complexity by the use
of abstraction, inheritance, and polymorphism. A Distributed Object Management System
(DOMS) is a system that uses DOM technology.
In Figure 12, we illustrate a workflow implementation using a DOMS. The DOMS pro-
vides interoperability among two HAD systems (OntosTM and SybaseTM DBMSs) and a
commercial WFMS (Lotus NotesTM). In addition, the DOMS provides interoperability
and reuse for workflow tasks that are represented as DOMS objects. The workflow in our
example groups and presents multimedia information for the reviewers of a conference
paper.
In this example, the Sybase database contains relations that include the name, address,
telephone number and other textual data for the people in the mailing list. Ontos is an
object DBMS that stores voice messages and pictures as objects. Both Sybase and Ontos
behave as servers in the DOMS. Lotus Notes is a DOMS client that serves as an interface
for the workflow users and stores workflow functionality that manipulates multimedia
data. In the DOMS, proxy objects are defined to represent (i) the mailing list data (e.g.,
records, relations, objects, or an entire database) and functionality (e.g., query processing)
provided by Sybase and Ontos, and (ii) the workflow tasks (to allow task reuse). Finally,
additional objects could be defined in the DOMS to create composite objects representing
composite tasks, or even workflows. When the workflow in our example is executed it
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invokes the task objects. The task objects invoke the multimedia objects (i.e., issues que-
ries over the multimedia data), and in response, the DOMS transparently retrieves the dis-
tributed data and returns these to Lotus Notes.
DOMS support for full interoperability simplifies the building of workflow implemen-
tations and the workflows themselves (e.g., by supporting task reuse and composition).
5.1.1 Technology status. To standardize DOMS architecture and services, software ven-
dors formed OMG. OMG’s Object Management Architecture [36] consists of a DOMS
component called Object Request Broker (ORB) [35] and the following three classifica-
tions of objects: Applications, Object Services, and Common Facilities [36] (illustrated in
Figure 13). The Common Object Request Broker Architecture (CORBA) [35] is the
DOMS architecture developed by OMG. An ORB is a CORBA-compliant DOMS. Appli-
cations are essentially the clients of the ORB environment. Object Services is a collection
of interfaces and objects that provide basic functions for using and implementing objects
(e.g., transaction services). Common Facilities is a collection of non-standard services that
provide general purpose capabilities useful in many applications. Applications access
server objects (i.e., services and common facilities) via the ORB. Note that server objects
themselves may be clients of other server objects.
There are several commercial products that comply with CORBA. Commercial ORBs
include Iona’s Orbix, DEC’s ObjectBroker, IBM’s DSOM, HP’s DOMF, and Sun’s DOE.
objects
proxy objects
DOMS
Lotus Notes
Ontos
Sybase
HAD system HAD system
get tel. and
address get
pictures display picture,
HAD system
tel. and address
get tel. and
address
Figure 12. An example of a simple DOMS providing interoperability for ad hoc workflow.
Object Services
Common FacilitiesApplication Objects
Object Request Broker
Transaction Services
Non-object
implementation
encapsulated
as object Object
Implementation
Figure 13. Object Management Architecture.
143
5.2. Customized transaction management (CTM)
CTM can support specific correctness, reliability, and functionality requirements for
each workflow application. To define CTM precisely, we first characterize the transac-
tional capabilities of the HAD systems workflow applications need to access assuming
that a DOMS is used to integrate HAD systems and WFM.
From the perspective of transaction management, objects integrated by a DOMS fall
into one of the following categories:
Transactional objects representing data and functionality in HAD systems that support
transactions. Any object that implements its own transaction management mechanism
(TMM) is included here. For example, this category includes DBMSs as well as those
file systems and programming language systems, e.g., Argus [26], that provide trans-
action support similar to that provided by a DBMS. We refer to DBMSs and all other
systems in this category as Local Transaction Management Systems (LTMSs).
Transactionless objects that represent data and functionality in HAD systems that do
not support transactions. Local systems in this category may be multi-threaded (e.g.,
file systems) or single-threaded (e.g., word processors, spreadsheets, simple pro-
grams). Multi-threaded local systems may provide some built-in concurrency control.
Commercial WFMSs belong in this category.
For example, in the DOMS and HAD systems in Figure 12, the Ontos and Sybase
DBMS are LTMSs. The databases, relations, tuples, and objects maintained by the
DBMSs, and/or the DBMSs themselves, are transactional objects. Lotus Notes is a trans-
actionless local system. Lotus Notes data and functionality, and the workflow implementa-
tion are transactionless objects.
To ensure the correctness and reliability of workflows accessing multiple transactional
and/or transactionless objects, each workflow application must be associated with a trans-
action model that defines the correctness and reliability required by the workflow. DBMSs
and TP monitors provide the ACID transaction model as a default to all applications using
their transaction management services. This basic transaction model requires enforcement
of all ACID properties (i.e., atomicity, consistency, isolation, and durability), e.g., allows
application to interleave as long as they produce results equivalent to an non-interleaved
execution. However, the ACID transaction model is not appropriate for many workflow
applications. For example, since the ACID transaction model enforces task isolation it
does not permit task cooperation. Therefore, it is too restrictive for workflows that require
task interaction.
CTM is the technology that satisfies these requirements. In particular, CTM supports
the definition and enforcement of ETMs that are:
1. application-specific: support workflow applications that have specialized requirements
for correctness, reliability, and functionality (e.g., require task cooperation)
2. user-defined: define constraints that are not built into the code of the TMM that
enforces them, since application requirements and object-provided guarantees may
change
3. augmented: require correctness and reliability capabilities that may not be supported
an object (and the corresponding HAD system)
4. multi-system: support applications that require access to objects maintained by multi-
ple HAD systems
Since these extend the ACID transaction model typically supported by DBMSs and TP
144
monitors, we refer to any transaction model that has at least one of these properties as an
extended transaction model (ETM).
Application-specific ETMs define the correctness and reliability requirements of appli-
cations implementing workflows. Transactional workflows are workflows supported by an
ETM that defines workflow correctness and reliability criteria. In particular, mapping
workflows to extended transactions involves [15]:
1. mapping workflow tasks to constituent transactions of an extended transaction sup-
ported by an ETM,
2. mapping workflow structure to an extended transaction structure supported by the
same ETM as (1), and
3. ensuring that workflow execution obeys the correctness criterion defined by the ETM.
Typically, workflow requirements are so diverse that no single ETM is sufficient to
meet the needs of all workflows.
The need for introducing ETMs to extend the traditional (ACID) transaction model
typically supported by DBMSs to allow additional application functionality (e.g., permit
task collaboration and coordination as it is required by ad hoc workflows) and improve
throughput (e.g., reduce transaction blocking and abortion caused by transaction synchro-
nization) has been recognized for some time. Several ETMs have been proposed (refer to
[10,16] for frameworks for defining and comparing ETMs, [13,12] for several representa-
tive ETMs, [43] for a representative model and specification that support application spe-
cific transaction properties, and [7, 5, 15, 20, 39] for views on relationships between
workflows and ETMs). However, many of these ACID transaction model extensions
resulted in application-specific ETMs offering adequate correctness guarantees in a partic-
ular application, but not ensuring correctness in others. Furthermore, an ETM may impose
restrictions that are unacceptable in one application, yet required by another. If no existing
ETM satisfies the requirements of an application, a new ETM must be defined to do so.
We give an example in the following section.
ETMs must be user-defined (not built-in) to effectively support: (i) a variety of transac-
tional workflows with diverse and possibly conflicting ETMs, and (ii) ETM changes that
may result from the evolution of a workflow and experience with its correctness and reli-
ability requirements (e.g., correctness constraints may be relaxed or imposed as we gain
more experience with an application). Traditionally, a system developed for a particular
application was designed to provide a built-in transaction model supporting application
requirements. In such systems, selecting an appropriate ETM was the responsibility of the
system designer. A DOMS or WFMS that supports a single built-in ETM cannot satisfy
the requirements of many diverse transactional workflows and cannot take advantage of
application experience in the (re)definition of the workflow ETM.
Defining an augmented ETM involves comparing the ETM correctness requirements
with the correctness guarantees provided by the HAD systems to determine whether the
ETM can be enforced by the local HAD systems. If the local HAD system cannot enforce
an ETM, CTM provides additional correctness and reliability guarantees that complement
those provided by the HAD system and together meet ETM requirements. For example,
consider the DOMS in Figure 12 and a transactional workflow that requires correctness
and reliability guarantees similar to those provided by ACID transactions. To satisfy the
workflow requirements CTM must provide ACID transactions over transactionless objects
in Figure 12.
145
The problem of supporting multi-system transactions has been partially investigated in
research on transaction management in multidatabase systems [19,8]. However, unlike
multidatabase transactions, transactional workflows may not consist of ACID transactions
and may have more than two levels of transaction/task nesting [43,39,12].
5.2.1 Specification of transactional workflows. Specification of transactional workflows
involves the specification of the ETMs that define their correctness criteria and structure.
ETM specification is based on the observation that extended transactions consist of a set
of constituent transactions (corresponding to the workflow tasks) and a set of transaction
dependencies between them (corresponding to the workflow structure and correctness cri-
terion). If a transactional workflow involves nesting, the constituent transactions of a
transactional workflow may be extended transactions themselves. Each transactional
workflow T has the following two kinds of transaction dependencies:
Intra-workflow transaction dependencies that define the relationships between the
constituent transactions of T.
Inter-workflow transaction dependencies that define the relationships between T and
all other transactional workflows
To illustrate transaction dependencies, consider again the “New Service Provisioning”
workflow illustrated in Figure 2. To simplify the discussion, suppose that T is the subset of
the “New Service Provisioning” workflow that includes only tasks T1, T2, and T3. In par-
ticular, assume that T is executed when a telephone company customer requests telephone
service installation. Task T1 performs a transaction that registers billing information in the
customer database. Tasks T2 and T3 execute transactions that perform two alternative line
provisioning functions. Only one of the provisioning tasks should be allowed to complete
as either will result in a completed circuit, i.e., a set of lines and equipment that connects
the customer to a telephone network. T2 attempts to provide a connection by using exist-
ing facilities such as lines and slots in switches. If T2 succeeds, the cost of provisioning is
minimal, i.e., the requested connection is established by allocating existing resources.
However, a successful completion of this activity may not be possible if the facilities are
not in place or if the capacity of existing facilities is exhausted. T3 achieves the same
objectives as T2 but involves physical installation of new facilities. Thus, T3 has a higher
cost than T2. Since T3 is needed only if T2 fails, T2 and T3 are contingency transactions.
The first category of intra-workflow transaction dependencies are transaction state
dependencies. Dependencies in this category are conditions on transaction state that define
the execution structure of transactional workflows. Defining intra-workflow transaction
state dependencies involves using transaction semantics (e.g., Begin, Abort, Commit) to
specify the ordering of workflow tasks. Such specifications that are more precise than
those allowed by the workflow specification languages WFMS typically provide. Figure
1
2
T1T2T3dependency
4
5
3
Figure 14. Dependencies that result from the execution structure of transaction T.
146
14 depicts the dependencies that define the execution structure of T assuming that T2 and
T3 cannot begin before T1 commits and that T2 and T3 can execute concurrently.The con-
stituent transactions of T have the following transaction state dependencies:
1. T2 cannot begin before T1 commits
2. T3 cannot begin before T1 commits
3. T3 cannot commit before T2aborts
4. T3must abort if T2 commits
5. T3 cannot begin after T2has committed
The second category of intra-workflow transaction dependencies are correctness
dependencies that specify which concurrent executions of transactional workflows pre-
serve consistency and produce correct results, thereby defining a correctness criterion.
Correctness dependencies include:
Serialization dependencies specify whether operations performed by a set of transac-
tional workflows must be serializable [9].
Visibility dependencies define whether operations performed by a set of transactional
workflows must be recoverable, cascadeless, strict, or rigorous [9,8].
Cooperation dependencies define whether a set of transactional workflows may per-
form specific operations on specific objects without restrictions.
Temporal dependencies that specify a set of transactional workflows must perform
operations in a particular temporal order [18].
The following dependencies are sufficient to ensure correctness of the transactional
workflow T in our example:
inter-workflow transaction serialization dependencies: The operations performed byT
and the operations performed by all committed transactional workflows must be serial-
izable. Note that this dependency does not require the constituent transactions of T to
appear atomic to each other.
intra-workflow transaction cooperation dependencies: The two contingency transac-
tions T2 and T3 need not appear atomic to each other.
The cooperative dependencies between T2 and T3 may result in a situation in which
both transactions are able to construct complete circuits using the same line(s) and/or
equipment. Since circuits require exclusive access to their lines, this will be unacceptable
for many other provisioning workflows. However, the semantics of this particular tele-
communications application permits any number of alternative transactions like T2 and
T3, as long as only one of them is allowed to commit and use the lines.
5.2.2 Technology status and research towards supporting CTM. Commercial DBMSs,
TP monitors, and multidatabase systems currently support only a small set of generic
ETMs (e.g., flat, nested, transaction consistency, cursor stability, uncontrolled reads). The
CORBA transaction service [37] is essentially a TP monitor. Thus, it is subject to the same
ETM limitations as the other TP monitors. Except for multidatabase transaction support,
none of these commercial products provides application-specific or user-defined ETMs.
The CTM concept, and research for developing technology to provide CTM, are rela-
tively new [17,5]. The Transaction Specification and Management Environment (TSME)
[17] is an example of a research effort for developing CTM technology. To support the
specification of ETMs, and the configuration of corresponding transaction management
mechanisms, the TSME provides a transaction dependency specification facility (TDSF)
147
and a corresponding programmable transaction management mechanism (PTMM). The
TDSF accepts specifications of ETMs expressed in terms of dependencies between the
kinds of transactions allowed by each ETM (as described in Section 5.2.1). The program-
mable TMM supports the implementation of ETMs, i.e., provides an environment in
which to execute transactional workflows and ensures the preservation of their dependen-
cies/ETMs.The TSME framework for ETM specification is described in [16]. The TSME
architecture and programmable TMM are discussed further in [17]. The ASSET system
[5] is another research effort for supporting application-specific ETMS. ASSET provides a
PTMM facility but does not deal with object/HAD system autonomy.
6. Conclusion
Workflow is an intuitive and powerful paradigm for capturing business processes, rea-
soning about them, and using process specifications to produce corresponding implemen-
tations that are supported by the information systems. However, the scope of solutions
provided by commercial WFMS is limited, e.g., they only support document/form/image-
centered processes, CSCW and office automation applications. Furthermore, many
WFMS products do not support workflows that need functionality and data in legacy HAD
systems, do not address efficient HAD system integration and interoperability, and do not
ensure the correctness and reliability of workflow execution in the presence of concur-
rency and failures.
Workflow research is also fragmented across multiple disciplines, such as CSCW, com-
puter-human interaction, imaging, and databases. The lack of interdisciplinary workflow
research has hindered establishing a common understanding or an understanding of the
different perspectives. For example, database researchers view workflows as information
processes and do not consider the human aspects of the business process implementation.
On the other hand, CSCW researchers ignore the role and importance of information sys-
tems. Since the vision of WFMSs is to support business processes that span entire organi-
zations or multiple organizations, and involve tasks that are performed by humans as well
as information systems, workflow requires technology involving the integration of tech-
nology from all these research areas.
In this paper, we discussed the requirements a computing environment supporting
workflows needs to satisfy. Furthermore, we described the reasons we believe WFM,
DOM, and CTM technologies should be integrated, and gave an overview of the technol-
ogy status and research in progress in these areas. Figure 15 depicts the dependencies
workflow requirements for computing infrastructure:
support interoperability between HAD systems
support distribution
cope with evolution, replacement and addition of HAD systems
ensure workflow correctness and reliability
support workflows corresponding to business processes
support workflow change as business processes change
Distributed
Customized
Transactional
Supports
Transaction
Management
Workflow
Management
Object
Management
Figure 15. Integration of DOM, CTM, and WFM to support transactional workflows.
148
between WFM, CTM, and DOM in providing a computing infrastructure that supports
fundamental workflow management requirements.Using commercial software available
today to develop such a workflow infrastructure may involve an open (extensible) WFMS,
a commercial ORB, and a TP monitor. CORBA products and XT/XA compliant TP moni-
tors are the current state of art for DOM and multi-system transaction processing, respec-
tively. OMG has recently integrated TP monitor technology by standardizing the OMG
transactions services. Unfortunately, most WFMSs are not CORBA compliant. TP moni-
tors do not provide CTM functionality required by many workflows, since TP monitors
provide only a few built-in transaction models. Therefore, supporting organization-wide
workflows today requires the development of software adaptors for bridging CORBA and
commercial WFMS architectures and services, and relying on software that operates out-
side the control of a TP monitor for CTM functionality. Although many difficult problems
must be solved before the workflow management technology becomes mature, the work-
flow concept is a compelling vision for research and commercial development.
Acknowledgments
We thank Gail Mitchell, Sandy Heiler, and Frank Manola for their wonderful com-
ments and suggestions.
Notes
1. Workflow implementations can control human tasks by directing humans to perform tasks as specified by
the workflow. Workflow implementations can also coordinate human tasks in that they facilitate the
exchange or coordination of business process information used by humans.
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Appendix A: Commercial Product and Company List
Action Workflow Action Technologies 1301 Marina Village Pkwy., Suite 100, Almeda, CA
94501, 800-WORKFLO. 510-521-6190
Amadeus Amadeus Software Research Inc. 12 Owen Court, Irvine, CA 92715, (714)
725-6400, email: amadeus-info@amadeus.com
Beyond Mail Beyond, Inc. 800-845-8511, 617-229-0006, fax: 617-229-1114
COHESION Team/SEE Digital Equipment Corp. 800-344-4825, 508-493-5111, fax: 508-493-8780
Design/IDEF Meta Software 125 Cambridge Park Road, Cambridge, MA 02140, 617-576-
6920
EPIC Computron Technologies
Extend + BPR Imagine That 6830 Via Del Oro, Suite 230, San Jose, CA 95119, 408-365-
0305, fax: 408-629-1251
Financial Stream Dun & Bradstreet Software 3445 Peachtree Rd. NE, Atlanta, GA 30326-1276,
[Accounting related], 404-239-2000
FloMark IBM 800-426-2968, 800-426-3333, 914-765-1900
FloWare and MapBuilder Recognition International 1310 Chesapeake Terrace, Sunnyvale, CA 94089,
800-999-5910, 408-743-4300, fax: 408-747-1245
Flowman Logical Software Solutions 7701 Greenbelt Rd., Suite 207, Greenbelt, MD
20770, 301-474-0285, fax: 301-474-0386
FormFlow Delrina Corp., 416-441-3676, fax: 416-441-0333
Higgins Enable Software 800-888-0684, 518-877-8600
ImageMover IMC, Inc.
InConcert XAIT (a division of Xerox Corp.) 3400 Hillview Ave., Palo Alto, CA 94303,
800-428-2995, 415-424-0111, fax: 415-813-7162
Keyfile Keyfile Corp. 22 Cotton Rd., Nashua, NH 03063, 603-883-3800, fax: 603-889-
9259
LinkWorks Digital Equipment Corp., 110 Spitbrook Rd., Nashua, NH 03062, (603) 881-
6146, fax: 603-881-2550
Mate Advanced Development Methods, Inc. 617-861-7848
Electronic Forms Designer Microsoft Corp. 800-426-9400, 206-882-8080
MSP/PM Software Design & Analysis Inc. 1113 Spruce Street, Boulder, CO 80302, 303-
444-9100. fax: 303-938-5005, email: riddle@sda.com
N-Dimensions Computron Technologies [Accounting related]
Navigator 2000/Workflow I. Levy and Associates 1600 Des Peres Rd., Suite 300, St. Louis, MO 63131,
314-822-0810, fax: 314-822-0309
Notes Lotus Development Corporation, Cambridge, MA, 617-577-8500, 800-346-
1305
ObjectFlow Digital Equipment Corporation, contact: Daryl Rosen, (603) 884-0882
OmniDesk Sigma Imaging Systems, Inc. 622 Third Ave., New York, NY 10017, 212-476-
3000, fax: 212-986-0175
Open/workflow Wang Labs One Industrial Ave., Lowell, MA 01851, 800-225-0654, 508-459-
5000, fax: 508-967-0828
Optika Optika Imaging Systems 5755 Mark Dabling Blvd., Suite 100, Colorado
Springs, CO 80919, 719-548-9800, fax: 719-531-7915
PCMS SQL Software Ltd Latton Bush Centre, Southern Way, Harlow, Essex CM18
7BL, UNITED KINGDOM, +44 (0) 279 451724 In the U.S., contact: SQL
Software Inc. 8000 Towers Crescent Drive, Suite 1350, Vienna, VA 22182,
(703) 760-7895, fax: 703-760-7899
PCTE Emeraude 152 Bureaux de la Colline, 92213 Saint Cloud Cedex, FRANCE,
+33 1 49 11 72 68, fax: +33 1 49 11 72 40
151
ProcessIt AT&T Global Information Solutions 1700 S. Patterson Blvd. Dayton, OH
45479, 800-225-5627, 513-445-5000, fax: 513-445-4184
Process Weaver Cap Gemini Innovation 7, chemin du Vieux Chene, 38240 Meylan, FRANCE,
+33 76 76 47 47, fax: +33 76 76 47 48 In the U.S., contact: Cap Gemini Amer-
ica, Software Engineering Productivity Practice, (212) 944-6464
Processwise ICL Wenlock Way, West Gorton, Manchester, M12 5DR, UK 061 223 1301
ProEDITOR International Software Systems, Inc. 9430 Research Blvd., Echelon IV, Suite
250, Austin, TX 78759 512-338-5700, fax: 512-338-5757
Redwood Walker Interactive Systems 303 Second St., Ste. 3 North, San Francisco, CA
94107 [Accounting related] 415-49597711, fax: 415-543-6338
Staffware Staffware Corp.
SynerVision Hewlett Packard Company U.S.: 800-63797740 Canada: Mississaugua,
Ontario, 416-678-9430 Japan: Tokyo, 03 5371 1351 Latin America: Lomas
de Chapultepec, Mexico, 525-202-0155 Australia/New Zeland: Blackburn,
Australia, 03 895 2895 Asia Pacific: Hong Kon, 852-848-7777 Europe/Africa/
Middle East: Geneva, Switzerland, 057-31-21-11
TeamFlow CFM, Inc.
TeamFlow - Client ICL 9801 Muirlands Blvd., Irvine, CA 92713, 714-855-5500, fax: 7149-458-
6257
Teamlinks Information Manager Digital Equipment Corp. 800-344-4825, 508-493-5111, fax: 508-493-8780
TeamSync Global Stream Corp. 800-685-7858, 206-858-7858
Team Talk Trax Softworks, Inc. 800-FOR-TRAX, 310-649-5800
TASC-Flow, TRAC-FlowSim , TASC-ControlTASC 55 Walkers Brook Dr., Reading, MA 01867 617-942-2000,
fax: 617-942-7100
ViewStar ViewStar Corp. 1101 Marina Village Pkwy., Alemeda, CA 94501 510-337-
2000, fax: 510-337-2222
Visual Workflo FileNet Corp. 3565 Harbor Blvd., Costa Mesa, CA 92626 800-FILENET, 714-
966-3400, fax: 714-966-3490
WorkFast ImageFast Software Systems 7926 Jones Branch Dr., Suite 260, McLean, VA
22102 800-899-6665, 703-893-1934, fax: 703-893-7499
WorkFlow Analyzer Meta Software Corp. 125 Cambridge Park Dr., Cambridge, MA 02140, 800-
227-4106, 617-576-6920, fax: 617-661-2008
Workflow Manager IBS 12626 Higg Bluff Drive, San Diego, CA 92130 800-346-2884, 619-772-
0273, fax: 619-792-5199
Workflow Manager Intergraph 800-346-7920, 610-7100, fax: 610-293-7117
Workflow Management System Cimage Corp. 3885 Research Park Dr., Ann Arbor, MI 48108, 800-241-4367,
313-761-6550, fax: 313-761-6551
Workgroup Templates Microsoft Corp. 800-426-9400, 206-882-8080
WorkMAN Reach Software Corporation 872 Hermosa Drive, Sunnyvale, CA 94086 800-
MAILFLO, 408-733-8685, fax: 408-733-9265
WorkManager, WorkRouter Hewlett-Packard Co. 300 Hanover St., Palo Alto, CA 94304 800-752-0900,
800-637-7740, fax: 800-333-1917
X Workflow Olivetti 22425 E. Appleway Ave., Liberty Lake, WA 99019 800-633-9909,
509-927-5600, fax: 509-927-5700
Appendix B: A comparison of five commercial workflow management systems
Next we compare five WFMSs. The comparison matrix reflects information available
from early 1994 product literature and conversations with sales and technical support staff
152
from the WFMSs’ respective vendors.
Feature\Product InConcert Staffware FloWare Notes ActionWorkflo
w
Trade Press Classification Production Administrative Production
Administrative
planned: Ad hoc
Ad hoc Production
Model Jobs, Tasks,
Roles, Users Case,
Procedure
Roles, Users
Map, Submap,
Activity,
Couriers
Tasks, Jobs,
Forms, Roles,
Users
Map, Loop,
Act, Roles,
Users
Client/Server Yes Yes Yes Yes Yes
Integration and Launch of
Office Applications Yes Yes Yes Yes Yes (via
Lotus Notes)
Scripting Language Yes (adminis-
trative func-
tions only)
Yes No (GUI only) No Yes
API Languages C, C++ No C, XDP AD 4GL C, C++ C, C++
Transport Mechanism RDBMS Email RDBMS Proprietary DB Email
Forms Creation
Environment No (planned
integration
with Notes)
Yes No Yes Yes
Dynamic Workflow
Modification Yes Yes Yes Yes Yes
Event Signaling
(Event-Action Triggers) Yes Yes Yes Yes Yes
Role/User
Administration Yes Yes Yes Yes Yes
Routing conditional,
parallel,
rule-based
conditional,
parallel,
rule-based
conditional,
parallel,
rule-based
conditional,
parallel,
rule-based
conditional,
parallel,
rule-based
Testing or Analysis Tools Yes Yes Yes No Yes
Graphical Workflow
Definition/
Manipulation
Yes Yes Yes Yes Yes
Alarm/Deadline/Priority Yes Yes Yes Yes Yes
Process Tracking Yes Yes Yes Yes Yes
Concurrency Control Yes
(Check-in/
Check-out)
Yes
(Pass by
reference/
value)
No No
(Replication/
Versioning)
Yes
(Primitive
Locking at
the Act level)
Support for Recovery No No No No No
Transaction Coordination
(e.g., 2PC) No No No No No
Security Auditability Auditability
Electronic
signatures
Authentication
Auditability
Authentication Authentication
Encryption
Authentication
Auditability
Authentication
Data Access
Control
Reporting Capabilities Yes Yes Yes Yes Yes
Keyword Search and
Workflow Querying Yes Yes Yes Yes Yes
OMG CORBA
compliant No No No No No
... Most of previous studies worked on architectural analysis but there is little being done on development of Language development of Workflow system with special emphasis on urban Traffic systems (Darbari & Bhaskar, 2008;Dvorak & Novak, 2003;Georgakopoulos, Homick, & Sheth, 1995;Panagos & Rabinovich, 1996;Knybel, 2005). We have shown the traffic flow by the help of Petri-net graphs Wang, 1998;Kepuska, Grubuz, rodriguez, Fiore, Carsten, converse, & Metcalf, 2008;Zhang, Lin, & Hsieh, 2008). ...
... The term "process" here indicates a set of tasks, or activities, linked together with the goal of creating a product, calculating a result, providing a service and so on. Hence, each task represents a piece of work that forms one logical step of the overall process (Georgakopoulos et al (1995)). The same definition can be used for scientific workflows composed of several tasks (or activities) that are connected together to express data and/or control dependencies (Liu et al (2004)). ...
... The workflow concept has evolved from the notion of progression in process automation in administration. Such processes have existed since industrialization and are products of a search to increase cost reduction by concentrating on the routine aspects of work activities (Georgakopoulos & Hornick, 2005). They typically separate work activities into well-defined tasks, roles, rules, and procedures which regulate most of the work in administration and the office. ...
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... The workflow concept has evolved from the notion of progression in process automation in administration. Such processes have existed since industrialization and are products of a search to increase cost reduction by concentrating on the routine aspects of work activities (Georgakopoulos & Hornick, 2005). They typically separate work activities into well-defined tasks, roles, rules, and procedures which regulate most of the work in administration and the office. ...
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... We augment an event based model [13] for workload enactment to support task replication, in which every time the status of the workflow changes (e.g. workflow starts, task completes) an event is triggered and the appropriate actions are performed. ...
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