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  <front>
    <journal-meta />
    <article-meta>
      <title-group>
        <article-title>L i n k i n g Het er o g en eo u s Co n c ep t u al Mo d el s t h r o u g h a Un i f y i n g Mo d el i n g Co n c ep t s On t o l o g y</article-title>
      </title-group>
      <contrib-group>
        <contrib contrib-type="author">
          <string-name>Janina Fengel</string-name>
          <email>janina.fengel@h-da.de</email>
          <xref ref-type="aff" rid="aff1">1</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Michael Rebstock</string-name>
          <email>michael.rebstock@h-da.de</email>
          <xref ref-type="aff" rid="aff0">0</xref>
        </contrib>
        <aff id="aff0">
          <label>0</label>
          <institution>University of Applied Sciences Darmstadt</institution>
          ,
          <addr-line>Haardtring 100, D - 64295 Darmstadt, +49 6151 16 8392</addr-line>
        </aff>
        <aff id="aff1">
          <label>1</label>
          <institution>University of Applied Sciences Darmstadt</institution>
          ,
          <addr-line>Hohe Strasse, D - 64807 Dieburg, +49 6151 16 9458</addr-line>
        </aff>
      </contrib-group>
      <abstract>
        <p>In this discussion paper we report on our ongoing work in applying Semantic-Web technologies for supporting business integration. Our method foresees the reengineering of conceptual models into ontologies for performing domain-semantics oriented matching. For linking models in differing modeling languages as well as different model types, we have developed a bridge ontology. The first results show the feasibility of our approach.</p>
      </abstract>
      <kwd-group>
        <kwd>eol&gt;Conceptual modeling</kwd>
        <kwd>semantic heterogeneity</kwd>
        <kwd>domain semantics</kwd>
        <kwd>modeling languages</kwd>
        <kwd>bridge ontology</kwd>
      </kwd-group>
    </article-meta>
  </front>
  <body>
    <sec id="sec-1">
      <title>1. INTRODUCTION</title>
      <p>
        The need for integrating conceptual models arises at the time of
process optimization, business (re-)engineering or generally in
business integration. Typical situations are reorganizations or
mergers, leading to process and application integration
challenges. Upon integrating the conceptual models describing
the business operations and the underlying IT-support,
heterogeneously used natural language for labeling model element
labels often hinders meaningful comparison. Furthermore, the
usage of different models in differing modeling languages usually
prevents automated support in aligning, linking or merging
models. Nevertheless, models to be integrated need to be
compared regarding the intended meaning of their elements and
their structure, whereas structural analysis cannot be performed
until successful alignment of the domain language [
        <xref ref-type="bibr" rid="ref13">13</xref>
        ]. Thereby,
especially naming conflicts hinder model integration [1; 14]. In
practice, often differing unrelated non-aligned legacy models
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      </p>
      <p>SBPM 2010, May 31, 2010, Heraklion, Crete, Greece.</p>
      <p>
        Copyright 2010 ACM 1-58113-000-0/00/0010…$10.00.
exist. There are efforts in matching models concentrating on the
aspect of model language semantics based on migration or
transformation from one modeling language into another [12; 7;
10], matching models via their meta models [
        <xref ref-type="bibr" rid="ref9">9</xref>
        ] or concentrating
on managing models of the same kind [
        <xref ref-type="bibr" rid="ref11">11</xref>
        ]. Thereby, the aspect of
heterogeneously used domain language is not addressed, instead
the model element labels are transferred and retained unchanged
for further use. Extending process models with semantic
annotations for easing consistent modeling and business-IT
alignment has been suggested, thus turning models into model
instances [16; 2]. For assigning element labels, the use of a
separately developed domain ontology has been proposed, similar
as in the suggestions for semantic business process management,
which rely on such a pre-defined business terminology [8; 4; 15].
It can assist in the creation of new models and provide the basis
for unambiguous element labeling as well as serve for mediating
the matching of existing models. However, the creation of a
common domain ontology or business terminology to be used as a
standard is usually time-consuming and cost-intensive.
Furthermore, comparing a model to the set standard is still
labourintensive work.
      </p>
      <p>For easing this workload, we propose to convert existing process,
data and organizational models into ontologies and provide
automated support for relating them by means of ontology
matching techniques. In this, our approach may serve as a
complement to the existing works in process matching as
outlined, as it offers a means to semantically integrate models of
different kind regarding the domain and modeling language
together. Additionally, through the semantics-oriented reuse of
the domain knowledge contained in models, over time the
collection of linked models may be taken as a skeleton semantic
domain or, more specifically, enterprise or business ontology. In
the following we continue with describing our method of
converting models into ontologies, followed by presenting the
bridge ontology specifically designed for enabling semantic
integration. We conclude with showing the method’s application
using a small example, closing with a brief discussion and outlook
onto our further work.</p>
    </sec>
    <sec id="sec-2">
      <title>2. ONTOLOGIZING MODELS</title>
      <p>
        By ontologizing models the business concepts’ semantics are
made machine-accessible, independent of the modeling languages
used. The creation of a model requires knowledge of the domain
language for naming the business concepts to be described as well
as the modeling language for describing their relations and sorting
them. Reversing this process allows us to decompose a model into
the domain semantics separately from the modeling language
semantics [
        <xref ref-type="bibr" rid="ref5">5</xref>
        ]. A model and its elements are split into two separate
ontologies in OWL DL, which together describe the model with
its model type and name and the model elements with their model
element types and labels. In the model conversion, all labels are
presently taken without further processing, so that not only terms,
but complete expressions are transferred. Often, domain
knowledge in the field of business processing lies in the
combination of objects and the execution of activities, which is
preserved this way. Basically, the suggested decomposition
method abstracts from the statement a model intends to do and
leaves the model as is for further active use. Figure 1 shows the
meta model of a thus decomposed conceptual model.
Thereby, the domain facts expressed in the natural domain
language are separated from the type of element they are
connected with. This type information resembles attaching
provenance information. For doing so, the idea of indexing the domain
facts in a manner similar to indexing in librarianship in form of
Topic Maps has been adopted. The model ontology on the left
side captures the domain knowledge in natural language as
owl:Classes and the relations between them as properties
with restrictions as needed. This model ontology links to the
model type ontology. For each modeling language a specific
Modeling Concept Ontology (MCO) has been developed,
containing parts of its meta model. The domain knowledge expressed in
the logical relations between model elements as the means for
setting the specific models’ element order is preserved together
with the domain facts in the model ontology, not in the MCO.
This conversion returns the element labels representing business
concepts as classes, thereby allowing a later ontology extension
with the concepts’ instances. Thus, the principle of conceptual
modeling in business is carried forward.
      </p>
    </sec>
    <sec id="sec-3">
      <title>3. THE UMCO AS A BRIDGE</title>
      <p>In principle, for any type of model an MCO can be developed. In
order to be able to link the ontologies resulting from the
conversion as described, the MCOs enable references between models of
the same type. For further enabling also the referencing of models
of the same kind, but different type as well as also models of
different kind, we use the Unifying Modeling Concepts Ontology
(UMCO), which we have developed specifically for this purpose.
It provides a unifying model concept for each type of modeling
concept with a similar intention. In this, it represents all relevant
element types for our approach, usable like a meta-meta model.
The UMCO and its MCOs serve for linking modeling concepts
without predefining relations beyond part-whole-definitions, as
this is done in the model ontologies.</p>
      <p>
        Input for the development of the UMCO has been drawn from
existing enterprise modeling languages and ontologies. Business
process modeling languages provide the means for describing
sequences of activities. They offer the idea of activities, either
being called activities, tasks, functions or actions, which start and
end with an event and are linked by flows. For the description of
the behavioral aspect of processes, the flows can be tied to logical
connectors for making decisions and showing alternative flow
paths [
        <xref ref-type="bibr" rid="ref12">12</xref>
        ]. In detail the semantics of process modeling languages
are not equivalent, so that models cannot be translated directly
without loss of information [
        <xref ref-type="bibr" rid="ref10">10</xref>
        ]. However, the fundamental
intensions of the concepts are comparable. The same observation
can be made for models describing static business information.
Conceptual data models can be represented as entity-relationship
models, UML class models or directly as OWL-ontologies.
Thereby, the entities of an ERM or classes of a class model
correspond to the classes of an ontology, while the attributes and
relationships correspond to the relations or properties in most
ontology languages [17]. Furthermore, UML class models can be
used for ontology modeling [6; 3]. For our purpose of integrating
models, we have defined general modeling concepts and declared
them equivalent to corresponding concepts in the various
modeling languages. In this, the UMCO further extends the meta
model shown in Figure 2.
The UMCO is extensible as needed for including further
MCOontologies. Developing MCOs for process, data and organization
models, or any other models, allows connecting knowledge not
only directly for model ontologies originating from the same
language space of the modeling languages, but additionally,
through the unifying modeling concepts, also knowledge from
model ontologies of different modeling languages. For example,
an EPC is defined compliant with an UML activity model and a
BPMN model, and these concepts are set to be equivalent to the
UMCO concept called UMCO:Process; EPC_MCO:Function
in an EPC, UML_AM_MCO:Action in an UML activity model and
BPMN:Task in a BPMN model are set to be equivalent to the
concept called UMCO:Activity. Accordingly, all modeling
concepts found in the various languages can be unified and
related, e.g. linking resources in process models such as
documents or participants to the data models detailing them.
      </p>
    </sec>
    <sec id="sec-4">
      <title>4. LINKING MODELS</title>
      <p>Usually, matching models is a major task. To ease this workload,
we partially automate this step by reengineering the conceptual
domain knowledge contained in existing models as shown and
relate the resulting model ontologies semantically for establishing
semantic correspondence between the model ontologies’
elements. As an implementation for semantic model integration in
the described manner, we develop the MODI (Model Integration)
Framework as an application of our method. Our framework is
realized in Java and can be accessed by a web service interface. It
consists of a core component, to which tools for mapping and
storage can be variably connected by adapters. Figure 3 shows the
architecture.
The focus of our work is on the realization of matching and
establishing domain-semantics based mappings between models.
Having performed the model conversions as described above,
ontology matching can be performed without merging any of the
input model ontologies. As the model ontologies obtained by
converting process models do not contain hierarchical or
mereologic relations, only element-based techniques return
meaningful mappings, best by tokenization and name matching.
For matching converted ERM and class model ontologies, also
structure-based techniques can be used, as here in most cases
subsumption and aggregation relations return exploitable
ontology structures. Since the domain facts are not transferred as
instances of their individual model type, it is prevented that
matchings return mappings between model element types. These
links are provided without creating workload for the matchers
through the introduction of the MCOs and the UMCO.
Furthermore, avoiding such an undesired hierarchical structure
focuses the matching efforts onto the domain language
independently of the original modeling language used. Figure 4
shows excerpts from two converted business process models from
the travel domain as an example. Each model depicts the booking
of services. The source model “Travel Reservation” is an EPC,
while the target model “Travel Booking” is a UML Activity
Model. They both depict the process of booking travel services,
however, the domain language differs.
The matching works could be performed successively as needed.
Results became available from the beginning, especially after
having included lexical background information from WordNet.
In our framework, all mappings found as a result of matchings are
stored in a repository as semantic correspondences. Thus, an
initial base is being established by means of automated tools. At
the time of using the resulting mapping ontology, the
automatically derived information is evaluated by its users. Even though
the need for manual work is reduced, the mappings found are not
always perfect, but may be ambiguous or incorrect [18].
Therefore, our system facilitates user participation by enabling
adding, editing and feedback provision for growth and
improvement over time. The evolving repository can be queried
for semantic correspondences. Thereby, a user may request
references for a specific term or directly compare two ontologies.
Figure 5 shows the prototypical screen of the results for a
comparison of the two example business process models.
With an increasing number of models included, first tendencies
towards commonly used terms can become obvious. An initial
terminological domain ontology emerges, consisting of the
various independent model ontologies, which are linked through
the mappings stored. This emerging ontology can be used at the
time of creating new models searching for a suitable element label
as well as for explaining the intended meaning in existing models
that need to be compared and related semantically.</p>
      <p>Combining the model ontologies with our modeling concepts
ontologies allows for searching for specific model types., e.g.,
searching for all EPCs available, as well as for models of all types
of a certain kind, e.g., such as process models either being EPC or
UML Activity Models, through utilizing the corresponding
unifying concept, here UMCO:Process, for detailing the query.
Alternatively, searches for UMCO:Activity return all business
operation steps. With the method described, not only models of
the same kind can be matched and related. Instead, linking
different models is possible as well with the help of the various
MCOs und the UMCO.</p>
    </sec>
    <sec id="sec-5">
      <title>5. DISCUSSION AND CONCLUSION</title>
      <p>Here we proposed an approach based on applying ontology
engineering techniques for achieving semantic integration of
conceptual models in the business domain. A method for reusing
existing conceptual models and relating the business knowledge
contained without huge manual efforts is shown. We have created
a way for reengineering such non-ontological resources for
meaningful relating and linking with the help of supporting ontologies
especially created for this purpose. The related models can be
analyzed and compared regarding the intended meaning of their
elements. The automatically produced results provide a basic
lightweight domain ontology without initial manual preparation
and creation efforts. By including user input, a possibility for
overcoming the shortcomings of automated knowledge computing
is presented, as human support is included for assessing and
improving the quality of the mappings found by way of
automated matching. The resulting mapping collection provides
support for the clarification of uncertainties and allows for
semantically integrating models of any type. Our system works as
a mediating medium and helps providing the grounds for
concentrating on the actual questions of process integration and
activity sequencing.</p>
      <p>The system presented here has been implemented as a
prototypical solution for the method developed and is being
evaluated. Its application has proven the conceptual strength and
practical relevance. Still, a number of aspects remain to be
researched. Since the system is based on coupling existing tools
for ontology matching and storing via adapters, evaluation
concerning their efficiency and performance is of interest. The
research concerning the comparison and combination of mapping
tools has to be concluded. Furthermore, as also is the case with
social software, our system needs a critical mass of users in order
to be useful. Hence, it needs to be proven that the method and
with this also our framework offers benefits. Overall, with our
approach of semantic model integration we hope to have shown
how the usage of Semantic-Web technologies may support
business modeling.</p>
    </sec>
    <sec id="sec-6">
      <title>6. ACKNOWLEDGMENTS</title>
      <p>Our work is supported by the German Federal Ministry of
Education and Research (BMBF) under grant no. 1728X07
MODI.
[17] Uschold, M. and Gruninger, M., 2004. Ontologies and
Semantics for Seamless Connectivity. ACM SIGMOD
Record 33(4), 58–64.</p>
    </sec>
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