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Applying Normalized Systems Theory in a Data
Integration Solution, a Case Report.
Hans Nouwens1(
), Edzo A. Botjes2, and Christiaan Balke1
1Sogeti Nederland, Vianen, the Netherlands
{Hans.Nouwens,Christiaan.Balke}@sogeti.com
2Xebia - Security, Hilversum, the Netherlands
ebotjes@xebia.com
Abstract. Enterprise Application Integration (EAI) becomes more im-
portant and non-evident when confronted with the growth of complex-
ity. The evolvability of the EAI solution itself decreases over time due
to Lehman’s law. This case report describes and evaluates the architec-
ture (model and principles), governance, solution design, and realisation,
which are based on the Normalized Systems Theory. There are indica-
tions that the realisation resulted in a mitigation of the eects of the
Lehman’s law, hence improving the evolvability of the created EAI solu-
tion.
Keywords: normalized systems · software architecture · case report
· enterprise application integration
1 Introduction
When implementing information systems, the main focus is on fast realisation
and deployment. Preventing complexity of integration between the information
systems is not the main priority [5,15].
The integration of applications, the exchanging of data between enterprise
applications, also known as Enterprise Application Integration (EAI) [10,3,5],
becomes more important and non-evident when confronted with the growth of
complexity of the application integration [5]. This often results in EAI becoming
distinct from application development with its own software used for performing
the task of integration [5]. There are various methods to integrate applications
[5]. Each methods has an unique complexity in their solution and an impact of
the complexity of the application that is integrated with the whole [5,7].
Lehman’s law of increasing complexity [9] states: ”As an evolving program
is constantly changed, it complexity, reecting deteriorating structure, increases
unless work is done to maintain or reduce it” [12, par. 6.2.2]. Normalized Sys-
tems Theory (NST) proposes a set of theorems/ principles to counter Lehman’s
law including the previously described complexity of EAI. NST argues that re-
duction of Combinatorial Eects (CE) will reduce the complexity of software.
Disconnecting the relation between the size of the application and the impact
of a change [1,15], will at least maintain a stable cost of change in a growing
Copyright © 2021 for this paper by its authors. Use permitted under Creative Commons License Attribution 4.0 International (CC BY 4.0).
2 Nouwens et al.
system. The theorems of NST are described in two books [11,12] and various ar-
ticles [13,14,4]. Description of NST implemented in software is limited available
[1,16,15] as is description on integrating applications using NST [5].
We want to add our experience with applying NST in a real life environment
to the available body of knowledge in the form of a case report following the
STARR format (Situation, Task, Approach, Result, Reection).
2 Situation
The case report subject is a Dutch university of applied science. The business
application landscape of this educational organisation evolved with little guid-
ance (organic). This resulted in many custom applications providing overlapping
functions and supporting undocumented information ows. Migrating this com-
plicated and interwoven application landscape to industry standard SaaS appli-
cations proved to be very time consuming, holding the organisation hostage in
its current situation.
Previous attempts to describe an architecture failed, mainly because of their
generic approach and lack of a clear vision on how to implement an evolvable
design.
3 Task
To help in this migration from custom applications to standard SaaS, in 2017 the
rst author was requested to write an architecture. An architecture that guided
a design for an evolvable data integration solution based on a hub-and-spoke
pattern with a central data storage hub.
One of the clients requirements was to make the design and solution able
to adapt to a changing environment, to be evolvable. Attention to potential
change drivers and possible combinatorial eects turned out to be one of the
main drivers behind the architecture and the solution designs.
1. The solution needs to support: multiple data sources and data targets,
multiple vendors, multiple communication patterns (pub/sub, etc), mul-
tiple security patterns (JSON Web Tokens, IP-Allow-List, etc), multiple
connection techniques (ODBC, REST/SOAP API, (s)FTP, http(s), e-mail,
SAMBA/NFS, etc), multiple le types (JSON, CSV, XLS(X), etc) and mul-
tiple (cloud) networks (on-premise, Private-cloud, Azure, AWS, GCP, etc).
2. The solution needs to support multiple frequencies of delivering data such
as a 24-hour bulk upload or small messages, based on events in a source
application.
3. The solution needs to support quality rules to prevent unqualied source
data to be distributed.
4. The solution needs to support ltering to ensure a data minimisation policy.
Applying normalized systems theory in a data integration solution 3
4 Approach
This case report contains our translation of the NST theorems [12, par. 12.2] into
an architecture for an EAI solution. In our experience, in the Dutch educational
sector the integration bus pattern is commonly used to realise EAI, especially
with of-the-shelf and Software-as-a-Service (SaaS) applications. This decision is
mainly based on the general conviction that the application of an ESB reduces
the number of connections between application from N(N-1)/2 to N as described
in [12, p. 275, g. 12.3].
However, we have not seen an application of the NST in this problem domain
in this sector.
For our evaluation and reection, we try to answer this question:
Does our architecture, applying our interpretation of the Nor-
malized Systems Theory, improve the evolvability of the created
EAI solution?
Author one fullled the role of architect, Author two fullled the role of
architect at other educational organisations with similar requirements, and not
directly involved at the case report subject. The third author was analyst and
engineer in realising and operating the solution during two years. The numbers
in this case report include the period when the engineer was involved as the
consulting architect when there was a limited involvement of the main architect.
Next to a number of personal observations and evaluations, we retrieved the
perceived eort to create new versions of the connections between the ESB and
the application. For this we consulted the previously hired developer, and the
developers, analyst and product owner currently working at the organisation.
If we were successful in preventing complexity, in the context of Lehmans
law, we should be able to see that the eort of changing a connection does
not increase together with the overall size of the system, the total number of
connections.
5 Result
The Integration Framework (IFW) is (1) a technical solution that integrates
multiple systems and data sources and (2) a framework of processes, controls and
agreements. The IFW system architecture describes the components, the way of
organising their relations and the principles guiding its design and evolution.
5.1 IFW system architecture
The IFW system consists out of the following three types of components: ‘source
pipelines‘, a ‘data-hub‘ component and ‘target pipelines‘ (see gure 1).
The ‘source pipelines‘ are responsible for the optimal ingestion of information
from the designated source systems and maintain integrity and actuality of the
4 Nouwens et al.
information in the ‘data storage‘. For each source system an instance of a source
pipeline is created. The ‘data-hub‘ is responsible for the availability of the infor-
mation. There is only one instance of the data-hub. The ‘target pipelines‘ are
responsible for providing data to systems that are not designated as the source
for this data. For each target system an instance of a target pipeline is cre-
ated. Together this creates the pattern of a ESB, plus a central data persistence
component.
Fig. 1. The Integration Framework (IFW) system model
The IFW system consists of the following sub-systems:
1. Source systems are connected to the IFW system to deliver part of it data
elements. The connection to the source systems is part of the scope of the
IFW, the source system itself is not. Each source system is connected to a
dedicated source pipeline.
2. Source pipelines consist of the following sequence of modules:
(a) The Adapters separate the connection specics of the source system from
the standards used within a pipeline. The adapter is the only sub-system
of the IFW system that directly interacts with the source system. It
handles functions like an IP-Allow-List, SSL-certicates, API-tokens, ac-
counts and passwords, le-transfers et cetera. A typical implementation
is based on an API gateway service. If the adapter receives individual
messages, it will buer them in a table.
(b) The Extractor retrieves the data from the result table of the Adapter
module. It converts technical formats (for example: JSON, XML, CSV)
to strong typed database records and values. The technical formats are
dictated by the source system. Type conversion may trigger a technical
error status and notications. The errors in the extractor are limited to
technical data integrity, job integrity and connection errors.
The extractor is responsible for storing a backup of the retrieved data
(les). The backup is used to restart the pipeline. Since every step can
be run independent it is possible that the extractor collects multiple sets
of retrieved data that accumulated while waiting to be processed by the
transformer step.
(c) The Transformer replaces values in the new data by updating it with ref-
erence tables from the meta system. Field quality rules check for allowed
Applying normalized systems theory in a data integration solution 5
values. Column quality rules count rows. Row counts can be compared
to a range of expected number of rows.
(d) The Combiner has a read-only database connection to the data-hub. It
changes the data model from based on the source system, to the shared
data model of the data-hub (also known as ODS3). It looks in the data-
hub at existing values and relational keys and creates new unique values
to be inserted. An unique key from the source system is maintained in
the data-hub to resolve future updates.
(e) The Loader creates or updates data in the data-hub. This is the only
IFW sub-system that updates or creates data in the data-hub.
3. The Data-hub contains the data that is to be distributed to target systems.
It has no historic record of previous versions like a data warehouse. The data
warehouse(s) of the organisation are considered as target system and source
system of the data-hub. The data-hub contains the most recent state of the
data-elements from the source systems.
(a) The canonical data model (CDM) of the data-hub must be able to an-
swer many questions by target systems, hence its independent, canonical
model.
(b) The technical data model (TDM) of the data-hub is the materialisation
of the Canonical Data Model [18].
The data-hub can consist of multiple types of data-storage solutions,
with each their own Technical Data Model, to ensure fullling all the
data requirements of the target systems. A single data-storage solution
would be in a 3NF4.
Examples of multiple data-storage solutions are (1) an on-premise SQL
master database with an SQL slave database in the cloud and (2) an
SQL database in combination with a Data-lake solution in the cloud.
(c) The Generic Views (GV) function as a facade between the data-storage
in the data-hub and the target pipelines [8]. The complexity of the
database model in the data-hub is hidden by the usage of views [2]. The
views are to be re-used by multiple outgoing pipelines. Generic Views
can not re-use other Generic Views as this would create a unwanted de-
pendency. Views are created to deliver grouped data on the level of a
complete business object5.
4. The Target pipelines are each created for each target system. They consist
of the following sequence of modules:
(a) The Selector combines several generic views from the data-hub. A subset
of the columns is selected to deliver only the required and allowed data
for this target system, enabling data minimisation policies.
3The term ODS is commonly used as Operational Data Store in relation to the data-
provisioning of a Data Warehouse (DWH) [6]. Currently it is more common to use the
term data-hub in the scope of data-provisioning to operational applications within
an organisation.
4See https://en.wikipedia.org/wiki/Third_normal_form
5An architectural name to describe a collection of attributes that together have a
meaning to business people, also known as information.
6 Nouwens et al.
(b) The Filter lters a subset of the rows, again enabling data minimisation
policies. Changes on both the column and row lters are explicitly un-
der governance of the privacy ocer6(CPO) and security ocer7(CISO)
[17]. Their policies determine the classication of the target system con-
nected to this instance of the pipeline [17]. Hence the data that is allowed
to be delivered to the target system. The list of attributes to be delivered
will be recorded in the data-delivery register, enabling GDPR8compli-
ance and processes.
(c) The Transformer again transforms from one data model (in this case the
CDM via the TDM) to the data model of the target system. It can also
apply changes to the data using the reference tables.
(d) The Adapter; the equivalent of the Adapter in the incoming pipeline. It
has the same dependency, but now to the target system. There are three
types of adapters present in the IFW solution: (1) a generic adapter using
API technology and services that resemble the Logical Data Model, (2)
a generic adapter using API technology and services that are specied
in a domain standard (for example: open banking api, open education
api) and (3) system specic adapter.
5. The Target systems receive data from the IFW solution. For every data-
element in the data-hub CDM there is a source system dened. Every other
system is a potential target system of this data-element. When a system
needs data that is not part of their assigned ownership, the required data-
elements are retrieved via a target pipeline.
6. Meta-data
Each of the modules maintains its own status in a globally available ta-
ble. The status ”is_enabled” in the Loader module enables testing of the
complete source pipeline and executing the quality rules, feeding back re-
sults based on production data without actually changing the data-hub and
feeding to target systems. This is a remediation of privacy concerns during
testing.
Severity levels of a failing quality rule will be logged. The next module will
use this to determine if it is allowed to start.
Log messages will be used to automatically report about any data elements
that failed, to the responsible owner of the source system. It enables quality
improvement of the reused information (not data) on an organisational level.
5.2 IFW governance architecture
The second part of the IFW is the governance processes and agreements.
Creating a pipeline starts based on a new target system that needs data. If
the required data is already available in the data-hub, only a target pipeline will
be created. If the required data is not available in the data-hub, the team looks
for a new existing source system to be connected with a new source pipeline.
6See https://en.wikipedia.org/wiki/Chief_privacy_officer
7See https://en.wikipedia.org/wiki/Chief_information_security_officer
8See https://eur-lex.europa.eu/eli/reg/2016/679/oj
Applying normalized systems theory in a data integration solution 7
For each pipeline the Information Manager (IM) signs an internal agreement
with the functional owner of the connected system. This agreement describes the
responsibilities of the stakeholders, the data quality requirements, privacy limi-
tations and includes a list of the data elements. The data ownership is delegated
from the functional owner of the source system to the IM. The IM signs a agree-
ment with the functional owners of the target systems (see Fig. 2). Compared
to the classic data-delivery agreements (spanning from source to target), this
decoupling aims to simplify the negotiations. The explicit use of the agreements
aims to increase the security, privacy and data quality awareness.
Fig. 2. Two separate relations and respective agreements.
5.3 Application of Normalized Systems Theory
The following customised interpretation of the Normalized Systems Theory (NST)
[12,4,14] was given to the designers:
The agility and changeability and hence the maintainability of a composite
system is determined by the diculty of changing the entire system. The focus
here is on preventing ripple (combinatorial) eects as an eect of changing a
sub-system.
1. Separation of concerns: a change must not have an impact on more than
one sub-system, this is also called functional loose coupling. Each sub-system
has only one responsibility.
2. Data Version Transparency: the version of an data element type is in-
cluded in the data element meta-data. Applications that process information
only use the version that they know.
3. Action Version Transparency: the version of an action element is in-
cluded in the action element. Applications invoke an action element only
with a version that they know.
4. Separation of States: after each action in a series, the intermediate result
is saved. Every sub-system is a real black box. Other sub-systems do not
need to know what the inside of another system looks like. They can ask the
sub-system what it does and what information can be delivered or requested.
Designers are given this set of architecture principles:
8 Nouwens et al.
1. Principle: Minimise dependencies
Rationale: Systems change, thus the integration system like the IFW will
change forever. These changes will be problematic if there are many depen-
dencies.
Implications: It can be cumbersome to prevent dependencies. This invest-
ment will pay for itself in the long run.
2. Principle: business objects are recorded in the Canonical Data
Model.
Rationale: Business objects consist of a considerable number of attributes,
rarely supplied by a single source system. In the Canonical Data Model
(CDM), the business objects with an unambiguous meaning are not related
to the model from a source system.
Implications:
(a) Business objects and their attributes are described in the CDM.
(b) Attributes of a business object can be provided by multiple source sys-
tems.
(c) The CDM is based on industry, general and market standards.
(d) The CDM contains only structured and machine readable elds.
3. Principle: Everything has a version.
Rationale: Explicit granting and simultaneous use of dierent versions gives
more exibility because systems and links do not have to be changed simul-
taneously when changing another system or link.
Implications:
(a) All elements, building blocks, steps, tables, views et cetera have a version.
(b) Every update of a building block or step with a functional dierence
gives a new version. Other building blocks never automatically use the
newer version.
(c) Versions exist side by side and are used simultaneously.
(d) All links (system calls, web services, FTP folders, references to tables,
etc.) explicitly refer to a version of an implementation.
(e) The (version) naming standard is applied and maintained.
(f) Implementations of new versions of elements are subject to a formal
change process.
4. Principle: All prescribed building blocks always exist and are ex-
clusively automated.
Rationale: Only if all building blocks in the IFW are designed and real-
ized, there is independence from all building blocks in the chain. Manual
processing steps are not allowed because this creates a dependency on an
(interpretation of a) person. The only meaning of the IFW is integration.
Implications:
(a) There is no building block that has presentation functions. This is re-
served for portals and user interfaces.
(b) There is no building block that realises business logic and business pro-
cesses. This is a task of the target or source systems or a special system
for automated business processes.
Applying normalized systems theory in a data integration solution 9
(c) There is no building block that realises reporting and analysis functions.
This is a task for target systems such as the data warehouse (DWH) or
Management Information System (MIS)
(d) Messages that lead to an error situation in the chain or in the target sys-
tems (both technical and functional) must be corrected by an adjustment
in the source.
(e) There is no functionality available for manually creating, changing or
deleting messages other than in the source.
5.4 Solution realisation
Based on an explicit requirements by the client, the design is created using
Microsoft components. Hence the adaptors being based on the Azure API man-
agement services and the databases implemented by a Microsoft SQL server.
These databases are on-premise because they mainly connect to on-premise sys-
tems. The IFW modules are implemented as SSIS packages9, usually created by
a BI developer. However, the architect and designer did choose for the use of
BIML10, a XML based language that is used to generate the SSIS packages. The
BIML scripts make use of meta-data in tables in the SQL server and maintained
with a Microsoft Access GUI. The quality rules are also generated during design
time. This generation is comparable to a pattern expansion process. In runtime,
a copied subset of the meta-data is used as reference tables (validation of allowed
values and replacement of values) and thresholds for the quality rules.
6 Reection
We collected and grouped the following observations on the realised IFW at this
organisation:
1. Applied architecture principles in respect to NST
(a) Principles 1 and 2 are translations of avoiding combinatorial eects re-
quirement and the separations of concerns theorem.
(b) Principle 3 translates the data and action version transparancy theorem.
(c) Principle 4 is based on anticipated changes of adding functionality. The
chosen tactic is to include all possible building blocks from the start,
even if they initially do nothing. Adding functionality later is limited
to enabling functions in the empty building blocks, not changing the
structure and relations.
(d) There is no principle that translates the separation of states theorem.
This is part of the IFW architecture model that describes the building
blocks, the way they handle data locally and handle state using shared
meta data.
2. Applied architecture principles in respect to building the solution
9See https://en.wikipedia.org/wiki/SQL_Server_Integration_Services
10 See https://en.wikipedia.org/wiki/Business_Intelligence_Markup_Language
10 Nouwens et al.
(a) Although the solution designers and developers were given freedom to
interpret the principles themselves, they frequently requested guidance
by an architect.
(b) Instead of the term ”preventing combinatorial eects” the team used the
term ”blocking domino eects”.
3. Solution design of module size
(a) We created expander scripts to generate modules as described in the
system structure (see Fig. 1). The size of these atomic elements of the
system is too large. This results in some repetition of the sub-functions
within a pipeline module and in combinatorial eects on the lowest (SSIS
package) level. Improved examples for the smallest elements could be:
i. reading the status from the meta-data and deciding if the module is
allowed to start
ii. application of quality rules
iii. replacing a value
iv. copy a value (database table to database table)
v. (re)creating result tables
vi. writing status or logging
4. Applied solution in respect to the data-hub
(a) A 3NF for the data-hub is cumbersome to design. There have been dis-
cussions to apply a dierent data model form such as a snow ake. A
supporting argument would be that this form is easier to generate based
on meta-data. This is not tested nor implemented as it would impact the
design of then existing loader modules. This is already a combinatorial
eect in the current architecture and design. However, the generic views
module as described in the design will act according to the Separation
of States theorem, eectively stopping the combinatorial eects to the
outgoing pipelines. This separation allows for a incremental update of
the data-hub.
(b) The architecture describes the data-hub and the 3NF as a Canonical
data model (CDM). During design we recognised that the generic views
of the data-hub are the CDM. The 3NF database design should be seen
as part of the black box of the data-hub.
(c) The use of meta-data, both during design time and run time is not
optimal. On the one hand using the same database tables in development
and production is out of the question. On the other hand, making copies
introduces duplicates and unwanted complexity.
5. Applied solution in respect to adaptors
(a) Recognised combinatory eects: Adaptors highly depend on the technical
implementation of the source system. Views are dependent on the data-
hub design. During the design phase these eects are recognised. Detailed
measures are taken to ensure the eect is only related to the next module.
This is preventing further domino eects. The combiner and loader both
depend on the (canonical and technical) data model of the data-hub.
This cannot be prevented as the combiner converts the incoming data
Applying normalized systems theory in a data integration solution 11
to the model of the data-hub, and the loader inserts and update data
within the constraints and design of the data-hub data model.
6. Governance
(a) Getting the responsible business owners to commit to the proposed agree-
ments (mandate and usage) turned out to be a hassle. It did cost a lot
of explaining to convince them of the necessity of the agreements. It did
also take some time to nd the right level of details for the description
of the data elements.
(b) the ability to separate the creation and deployment of source pipelines
from target pipelines is an improvement. In the applied agile way of
working the individual backlog items turned out to be close to a module
in a pipe line. Several tasks within this item could be worked on by
dierent developers. This increased the understanding on the progress
of the development.
6.1 Validating the observations
To validate our observations, we interviewed four people who where also directly
involved in the design and development of the system; The product owner, the
development manager, the senior designer/developer, and a developer/sysadmin.
At the start of each interview we briey explained Lehman’s law and the
goal of our paper and interview. We presented our observations 2a, 2b, 3a, 4a,
4b, 4c, 5a, 6a, and 6b for validation in the form of ”Can you agree that …?”
Observations 1a..d were skipped because these explain the mapping between
the NS theorems and the architecture principles and therefore not suitable for
validation by the interviewees. We added a question to retrieve insight in the
perception of the evolvability of the system: ”7: Now that the system has about
20 pipelines, compared to the beginning when the system had two pipelines.
What is your global impression: Has the eort of making a comparable change
stayed the same?”.
For each question the answers where limited to the following options: ”not
applicable” (for instance when the interviewee was not involved in that topic
and did not know an answer), and ”strongly disagree”, ”disagree”, ”agree”, or
”strongly agree”. By leaving out the option for a neutral answer, we forced the
interviewees to make a explicit choice. All interviews were done by author one
as interviewer, carefully using comparable wording.
Based on the summed scores, the interviewees conrmed all except observa-
tions 3a and 4a (see table 1).
Regarding observation 3a, about the module size in the solution design, that
it should have been designed smaller; The product owner and development man-
ager disagreed. The senior designer/developer strongly disagreed, even suggested
they should be larger. The developer agreed.
In respect to observation 4a, about 3NF being cumbersome to design; The
two managers both strongly agreed, giving arguments that it took a lot of time,
eort and thus money. The two developers both disagreed, giving arguments
12 Nouwens et al.
Table 1. Results of four validation interviews
that the 3NF was not easy but do-able and most of all necessary to be able to
deliver all possible combinations towards outgoing pipelines.
The added question (7) about the eort related to the system size was agreed
upon by all four interviewees.
7 Conclusion
This paper reports about an application of Normalized Systems Theory (NST)
in the context of a data integration solution. A summary is given of our inter-
pretation of NST, as given by the architect to the designers of the integration
software. This case report is part of the practitioners double learning loop.
In this case, the application of the Normalized Systems Theory helped the
practitioners to improve the adaptability of the data integration solution. In our
view it is denitely better but not perfect.
As the design team was unfamiliar with NST, the use of the NST theorems
within the context of an architecture model and architecture principles, indi-
cated the need for continuous decision-making support. Using the term ”blocking
domino eects” improved comprehension of the team’s design challenge.
The SSIS-packages, part of the Microsoft SQL suite, can be generated using
BIML. This case report indicates that this combination can be used as a Normal-
ized Systems Theory expander. However, the optimal module size is disputable.
Based on our validated observations we can state; There are indications that
this IFW design, and architecture principles, our interpretation of NST, discon-
nect the relation between the size of the application and the impact of a change.
Thus mitigating the eects of Lehman’s Law and improving the evolvability of
the created EAI solution.
Applying normalized systems theory in a data integration solution 13
8 Future Research
Based on the experience at this specic organisation, the IFW architecture was
applied and realised at other Dutch educational organisations. Each with dier-
ent technologies and various implementation strategies. Future research could be
collecting these individual use cases and combine it with a post implementation
questionnaire to compare the perceived (added) value of the IFW architecture
and the NST application.
Research could be done to nd the smallest element to generate using the
BIML scripts.
Research could be done to automate the generation of the Technical Data
Model of the data-hub. This would save a signicant amount of time and eort.
Acknowledgements
We would like to thank the involved Dutch educational organisations in sup-
porting the collaborative open discussion on the topic of enterprise application
integration, and willing to exchange the knowledge between their organisations.
We also would like to thank our (former) colleagues at Sogeti for reecting on
our concept architecture descriptions and adding their views and experiences.
We see the creation of IFW as an example of combining academic research,
the operational application of this knowledge in production and sharing the
experience back to the academic eld.
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