Tobias Unger’s research while affiliated with University of Stuttgart and other places

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Publications (31)


Performance Optimizations for Interacting Business Processes*
  • Conference Paper

March 2013

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18 Reads

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5 Citations

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Choreographies describe the interaction behavior of processes at design time: a choreography defines when messages have to be exchanged between the involved processes during their runtime. In the context of Web services and the de-facto workflow language BPEL, SOAP is used to encode the messages. When complex messages are exchanged between the processes, this can become costly and time consuming with respect to the overall execution time of a choreography. In this work, we suggest three different performance optimization techniques for workflow engines to reduce the number of message exchanges between the interacting processes and hence, to decrease the execution times and costs of the choreographies: intra-engine transport, service request caching, and inline execution. We describe how these techniques are implemented in a workflow engine. Performance measurements are carried out to determine the performance improvements that are achieved with each optimization technique. We further show that the optimizations also affect the energy consumption of the workflow engine.


Six Strategies for Building High Performance SOA Applications

May 2012

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29 Reads

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2 Citations

The service-oriented architecture (SOA) concepts such as loose coupling may have negative impact on the overall execution performance of a single request. There are ways to facilitate high performance applications which benefit from this kind of architectural style compensating the caused overhead significantly. This paper gives an overview on six high level strategies to improve the performance of SOAs with a central service bus and presents how to apply them to build high performance service-oriented applications without corrupting the SOA paradigm and concepts on the technical level.


Figure 5: Sketch of Pseudonymizer of Critical Data. 
Cloud Data Patterns for Confidentiality
  • Conference Paper
  • Full-text available

April 2012

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266 Reads

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24 Citations

Cloud computing enables cost-effective, self-service, and elastic hosting of applications in the Cloud. Applications may be partially or completely moved to the Cloud. When hosting or moving the database layer to the Cloud, challenges such as avoidance of disclosure of critical data have to be faced. The main challenges are handling different levels of confidentiality and satisfying security and privacy requirements. We provide reusable solutions in the form of patterns.

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Figure 1. Overview of Cloud Deployment Models and Application Layers
Figure 2. Taxonomy for Cloud Data Hosting Solutions  
A Taxonomy for Cloud Data Hosting Solutions

December 2011

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651 Reads

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10 Citations

Cloud computing allows reducing capital expenditure by using resources on demand. We investigate how to build a database layer in the Cloud and present pure and hybrid Cloud data hosting solutions. The solutions are organized in a taxonomy. The properties used for organization are: application layer, deployment model, location, service model, data store type, and compatibility. Using the taxonomy, existing Cloud data hosting solutions are categorized.


A classification of BPEL extensions

November 2011

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12 Reads

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21 Citations

Journal of Systems Integration

The Business Process Execution Language (BPEL) has emerged as de-facto standard for business processes implementation. This language is designed to be extensible for including additional valuable features in a standardized manner. There are a number of BPEL extensions available. They are, however, neither classified nor evaluated with respect to their compliance to the BPEL standard. This article fills this gap by providing a framework for classifying BPEL extensions, a classification of existing extensions, and a guideline for designing BPEL extensions.


An event model for WS-BPEL 2.0

September 2011

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105 Reads

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7 Citations

This report presents an engine-independent WS-BPEL 2.0 event model. It supports both passive monitoring and active control of process execution by external applications. Some of the assumptions in the presented event model are inspired by a particular implementation, e.g. fault handling and compensation; however they are kept as general as possible, so that they can be mapped on other engine-specific approaches to tackle faults and support compensation. In addition, the report draws on the experience of some of the authors in business process management and software development. The overall BPEL event model consists of a set of event models for the different types of BPEL entities that change their states: processes, process instances, general activities, scope activities, invoke activities, loops, links, variables, partner links, and correlation sets. The event model is used by the authors of the report in several projects, all utilizing process life cycle events in different scenarios.


Dynamic Composition of Pervasive Process Fragments

July 2011

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13 Reads

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23 Citations

A critical aspect for pervasive computing is the possibility to discover and use process knowledge at run time depending on the specific context. This can be achieved by using an underlying service-based application and exploiting its features in terms of dynamic service discovery, selection, and composition. Pervasive process fragments represent a service-based tool that allows to model incomplete and contextual knowledge. We provide a solution to automatically compose such fragments into complete processes, according to a specific context and specific goals. We compute the solution by encoding process knowledge, domain knowledge and goals into an AI planning problem. We evaluate our approach on different scenarios stress testing the main characteristics of pervasive process fragments.


Towards The Essential Flow Model

March 2011

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64 Reads

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2 Citations

Many of today's manufacturing projects are so complex that they cannot be conducted only by one company anymore. Current approaches for modeling inter-enterprise processes require an early decision on the way activities are connected. The modeler has to decide between control flow and message flow. This implies an early decision on the used IT-technology. We present a modeling approach where this decision is postponed to a later modeling phase. This enables modelers to concentrate on the essentials of the model.


Fig. 1. Fragments in BPMN 2.0  
Fig. 2. Example BPMN fragment  
On BPMN process fragment auto-completion

March 2011

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518 Reads

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3 Citations

Process fragments provide reusable granules of business processes to enable process modeling based on existing knowledge. Current verification tools cannot deal with BPMN process fragments and support complete BPMN processes only. To enable verification for BPMN process fragments, we sketch how a single BPMN fragment can be completed to a BPMN process, where additional gateways and start events are added.


Horizontal and Vertical Combination of Multi-Tenancy Patterns in Service-Oriented Applications

February 2011

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352 Reads

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88 Citations

Enterprise Information Systems

Software as a service (SaaS) providers exploit economies of scale by offering the same instance of an application to multiple customers typically in a single-instance multi-tenant architecture model. Therefore the applications must be scalable, multi-tenant aware and configurable. In this article, we show how the services in a service-oriented SaaS application can be deployed using different multi-tenancy patterns. We describe how services in different multi-tenancy patterns can be composed on the application level. In addition to that, we also describe how these multi-tenancy patterns can be applied to middleware and hardware components. We then show with some real world examples how the different multi-tenancy patterns can be combined.


Citations (26)


... However, the common standard modeling notations hardly utilize advanced models and features in dealing with events. For instance, the business process execution language Business Process Execution Language (BPEL) [52] treats events as messages and does not provide the modeler with the opportunity to define complex events within the model [53]. In contrast, BPMN explicitly includes the notion of events such as timers, signals or exceptions, but lacks the capability of handling or defining complex events. ...

Reference:

From Event Streams to Process Models and Back: Challenges and Opportunities
A classification of BPEL extensions
  • Citing Book
  • November 2011

Journal of Systems Integration

... We do so by focusing on a basic functionality of a process engine, that is managing the state of the process at any given moment. When a process is executed, each work item (namely, an instance of an activity in the process model) can be disabled (before its preconditions are fulfilled based on the process model), enabled (when according to the process model it is possible to start executing it), active, or completed [102]. As work items are completed, the state of the process changes and other work items become enabled. ...

An event model for WS-BPEL 2.0

... After manually modeling the choreography, the resulting model has to be transformed into an executable workflow. This has to be done as choreographies are not suited to be executed on a single workflow machine: unnecessary communication effort between the different workflows would slow down the execution time [39] and passing sensitive data over the wire, e. g., the database credentials, is not appropriate. Therefore, in this step, the choreography is automatically translated into an executable workflow model. ...

Performance Optimizations for Interacting Business Processes*
  • Citing Conference Paper
  • March 2013

... In this case, a health-based dataset related to cancer was used, sourced from the UCI repository, which houses datasets which are frequently utilised across a broad range of research [28][29] [30][31] [32]. The datasets were set as critical categories, meaning that data breaches in such data could damage the organisation or individual reputationally, with negative impacts on functional operations [33]. ...

Cloud Data Patterns for Confidentiality

... The SCS architecture corresponds to the highest level of the four-level SaaS maturity model [20], i.e., it is scalable, configurable, and multi-tenant-efficient. Multi-tenancy proficiency is also observed in the Integration microservice considering that the architecture can combine different multi-tenancy patterns [21]. ...

Combining Different Multi-Tenancy Patterns in Service-Oriented Applications
  • Citing Conference Paper
  • October 2009

... Against this background, we consider it important to investigate how coPM is impacted by the presence of Business Process Management Journal task uncertainty. Task analyzability may, for example, influence the comparison of tasks executed in different organizations due to different specifications of task execution, while task variety may be required to consider when comparing task performance between multiple organizations, for example, as unforeseen constraints of location, time or personnel resources restrict the task execution (Unger and Wagner, 2011). We expect both to be important for coPM to exploit commonalities and provide an opportunity to contribute to theory on IT-enabled inter-organizational learning (Scott, 2000). ...

Collaboration Aspects of Human Tasks
  • Citing Conference Paper
  • September 2010

Lecture Notes in Business Information Processing

... The event model neither allows for suspending a single activity nor signals such a suspension. Such a partial suspension is motivated by processes offering parts of themselves as subprocesses [16]. When adding such a feature, the state chart has to distinguish between long-running and short-running activities: long-running activities may be suspended at the states Ready, Executing, and Completing, whereas shortrunning activities may suspended during the states Ready and Completing. ...

The Subprocess Spectrum

... Eberle et. al. [49,48] introduce the concept of process fragment as incomplete process knowledge which can be dynamically stitched together at runtime. While their research focuses on the composition of process fragment, the research in this thesis underlines the concept, the application on BPEL, the extraction methods, and the query mechanism of process fragments. ...

Process Fragment Composition Operations
  • Citing Conference Paper
  • December 2010

... In the meanwhile, there are some other approaches tend to do forward recovery to heighten the level of fault-tolerance thereby to improve overall throughput of transactions. For example, a forward recovery strategy for process fragments was suggested in [6]. However, all these approaches only focus on data compensation or data dependency when a transaction fails. ...

Transactional Process Fragments - Recovery Strategies for Flexible Workflows with Process Fragments
  • Citing Conference Paper
  • December 2010

... The essential flow model [10] tackles the issue that modelers have to decide early which paradigm they follow when modeling collaborations. By following the orchestration paradigm the whole collaboration is specified within one consolidated process model where all tasks are connected through control flow. ...

Towards The Essential Flow Model