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Representation of UML Activity Models as Ontology

Ali Hanzala Khan, Abid Ali Minhas Moazzam Fareed Niazi Department of Computer & System Sciences Department of Information Technology

Royal Institute of Technology-KTH, Sweden University of Turku, Finland

{hanzala, aaminhas} @kth.se [email protected]

Abstract

Ontology is a conceptual model that is used to

represent the concepts in a domain and relationshipbetween the concepts. It can be used for sharing andreuse of the knowledge that allows humans and

machines to exchange diverse information. A process

is a series of activities that result in an outcome.

Processes can be shared and reused by creating a

repository that keeps all the information about them.Such a repository can serve us independent of the

domain for which a process is modeled. Process

modeling is a technique for the graphical

representation of a process. Among many process-

modeling techniques, UML Activity Model is acommonly used process-modeling notation and isadopted for our research. This research aims at to

provide a solution for representing UML Activity

Model as an Ontology expressed in OWL. A method is

proposed for this purpose that defines mapping rules

between a UML Activity Model and Ontology. Toevaluate the validity and usefulness of our research acase study is conducted. Military action scenario,

modeled using UML Activity Model, is taken as input.

Consequently they are mapped into ontology, thus

expressing behavioral knowledge captured in theprocess as OWL ontology.

1. Introduction

Process Modeling is the graphical representation of

processes that capture, manipulate store, and distribute

data between a system and its environment and amongcomponents within a system [1]. Such a model

identifies constructs that are used to define and

represent a process in graphical form. Commonly used

process models arePetri Nets [2], UML Activity model

[3], UML Sequence Diagram [4] andBPMN(Business

Process Modeling Notation) [5].

Ontology is a conceptual model which is used to

represent the concepts in a domain and relationship

across them [6]. Researchers propose the use of

ontologies for sharing and reuse of the knowledge that

allows humans and machines to exchange diverse

information [7]. OWL (Web Ontology Language) [8]

is a current standard for specifying such ontologies.

The UML behavioral models are process modelsthat contain information, which can be stored using a

knowledge representation format like ontology. A

process, business activity or workflow can be

transformed into ontology for this purpose. Such a

format will aid the information to be shared and reused

by domain experts without understanding the concepts

and notations of ontology.

Past research regarding UML Models to Ontology

transformations was limited to mapping UML Class

diagrams to Ontology [9-11]. Efforts like [9, 12, 13,

14, 15, 16] are successful to extent of mapping Static

Structural Models into ontology. Behavior models like

Petri Nets [2], UML Activity model[3], UML SequenceDiagram [4] and BPMN[5] that illustrates work flowand business processes are not significantly addressed.

UML Activity model is widely used approach for

process modeling. Consequently we have chosen this

model for our desired purpose. Currently, a limited

research is available on how we should represent the

behavioral knowledge captured in an UML activity

model using the same OWL ontology language.

2. UML Behavioral model to OWL

According to our proposed method, a UML activity

diagram is modeled in a UML modeling tool, forexample, Poseidon for UML, a UML based modeling

tool. The tool exports an XMI, which is embedded

with the behavioral knowledge expressed in a

particular UML activity diagram. This XMI serves as

input to mapping application as shown in Figure 1. On

the other hand we have target process ontology


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expressed in OWL. This ontology is specially modeled

to match the needs of our research.

The mapping rules are scripted in form of XML

Style sheet Language Transformation XSLT;XSLT is a

language for transforming XML documents into other

XML documents [17]. XSLT together with XMI

representation of UML activity diagram is used as

input to the mapping application. The output is OWL

ontology expressing the behavior knowledge

represented by activity diagram; Figure 1 depicts a

detailed overview of our proposed solution.

Figure 1. Proposed solution

2.1. Target Ontology

Translation of UML Activity Diagram into ontology

requires the use of predefined target ontology. Target

ontology needs to be expressive enough to capture the

information contained in a UML Activity Diagram.

There exist many process ontologies such as Open

Source Business Management Ontology [18], Biological Process Ontology [19], Software Design

Process Ontology [20] and Gene Ontology [21]. But

they are domain specific and are not readily usable for

representing a generic process. There are some otherontologies like A Process Ontology [22] and OWL-Sthat support generic process representation. None of

these can be used as it is for our research. But a

thorough examination reveals that OWL-S is very

suitable for the cause if we modify OWL-S to build our

target ontology.

OWL-S is an OWL based ontology proposed for

description of web services [23]. It enables automatic

discovery, invocation, composition and interoperation

of web services for software agents. OWL-S consists

of three parts i.e.service profile,service groundingand

service process model. Service profile tells what a

service does where as service grounding encloseinformation necessary for a user to interact with the

service. Process model describes the procedure for

service execution illustrating the input, output and

activities involved in course of action. Service process

model of OWL-S is closely related to what we need as

target ontology to capture the semantics of UML

activity diagram.

OWL-S process ontology is modified to obtain a

process ontology that will serve the purpose of this

research. We are excluding UAD-OWL target ontology

figure because of the space reason but its accessible

on one of the authors homepage at [24]. Following is

a summary of UAD-OWL target ontology.

Process class represents a process.Control Construct is a class concept with sub class

concepts Merge, Fork, Choice, Perform, Join and

Decision. These classes represent the UML activity

diagram control constructs.

Activity is a class concept with sub class concepts Atomic Activity and Composite Activity. Composite

activity represents the process as whole. Atomic

activity represents the activities or tasks to complete

the process. The sub class concepts of atomic activity

capture detailed information of each activity, for

example, time limit, loop etc.

List class concept has a sub class concept named asControl Construct List used to maintain the

information regarding the sequence of graphical

control constructs of a UML activity diagram.

UAD-OWL ontology will serve as a repository of

processes. It is capable of expressing the behavioral

knowledge represented by processes modeled using

UML activity diagram. This repository will facilitate

sharing and reuse of different processes. UML-OWL

can be viewed in an ontology-modeling tool such as

Protg [25].

2.2. Mapping Rules

This section describes how constructs across the two

models are related at conceptual level. This leads to

realization of correspondence between source model

and target model notations. Table 1 represents an

overview of the way control constructs of OWL

ontology map to UML Activity Diagram constructs.

A UML activity diagram can have six different

types of control constructs i.e. Fork, Join, Transition,

Decision, Merge and State. In UAD-OWL ontology

there is class concept Control Constructthat can servethis purpose. It has six sub classes named as Fork,

Choice, Perform, Join and Decision. Accordingly

Fork, Join, Transition, Decision, Merge and State from

UML activity diagram are mapped onto Fork, Join,

Transition, Decision, Merge and State class constructsof OWL respectively.

Table 1 summarizes the correspondence between

above mentioned constructs across two models.


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Type UML 2.0 UAD-OWL

Control Construct Fork Fork

Join Join

Transition Choice

Decision Decision

Merge Merge

State Perform

Activity State Action Task

Model Composite Activity

Table 1. Construct mapping at conceptual level.

A UML activity diagram models activities involved

in a process. The process modeled is labeled as Modeland each activity are labeled as State. Proposed

ontology has class concepts as Atomic Activity and

Composite Activity. State and Model constructs from

UML are mapped into Atomic Activity and Composite

Activity constructs of OWL respectively.

The association between vocabularies of the two

models, as shown in Table 2, tends towards the general

rules for transformation. These rules can be followed

for translation of UML Activity to OWL ontology.

Thus mapping at implementation level can beachieved. XML Metadata Interchange (XMI) is a

standard for exchanging metadata information via

XML. OWL is also a XML schema. All we need is to

transform one XML document to another XML

document. For that reason we have identified

relationship between UML metadata XMI tags and

OWL tags. Summary of the relationship between

source XMI and target OWL is presented in Table 2.

Table 2. Construct mapping at implementation level.

3. Related Work

Woong Kim and Kyong-Ho Lee propose a method

for Describing semantic web services: From UML toOWL-S [26], they are using XSLT to transform

activity model into ontology, Table 3 and Table 4

shows the comparison of Kims method with UAD-

OWL method mapping rules at conceptual and

implementation level respectively.

Table 3. Mapping rulescomparison at conceptual level

Table 4. Mapping rulescomparison at implementation level

4. Case Study

4.1. Base Object Models (BOMs)

The Simulation Interoperability Standards

Organization (SISO) focuses on facilitating simulation

interoperability across governmental and non-

governmental application worldwide. SISO has

proposed Base Object Models (BOMs) [27] as amethod to support and promote reuse of simulation

components.

Base Object Models (BOMs) provide a component

framework for facilitating interoperability, reuse, and

compatibility. The assumption behind BOMs is that

piece parts of models, simulations, and federations can

be extracted and reused as modeling building or

components. The interplay between simulations can be

captured in the form of reusable patterns. The patternof interplay is sequence of events between simulation

elements. BOMs capture the representation of the

pattern. Simulation conceptual model found in BOMs

contain information on how conceptual entities andconceptual events, representing real world entities,

relate or interact with each other in real world. This

information is illustrated in the form of patterns of

interplay andstate machines.

UML-XMI OWL

Construct XML Tag Construct Kim

XMLTag

UAD-OWL XML

Tag

Model Process X

Join Join X

Decision

Decision X

Type UML 2.0 Kim-OWL UAD-OWL

Control

Construct

Fork Split Fork

Join Join Join

Transition X Choice

Decision Choice Decision

Merge X Merge

State X Perform

Activity

State X Action Task

Model X CompositeActivity

UML-XMI OWL

Construct XML Tag Construct UAD-OWL XML Tag

Model Process

Fork Fork

Transition Choice

Merge Merge


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4.2. Test Case

This section is about the transformation of activity

model for the Target Entity of a Weapon Effects BOM

in to OWL.

4.2.1. State machine of the target entity

In this case study, the only conceptual entity

identified for fulfilling the state machine is the

TargetEntity. The details of a conceptual entity, such

as TargetEntity, are defined separately within a BOM.

Each state transition is carried out by an exit action.

Details of the exit actions, such as Weapon Fire

Action, Munition Detonation Action, and Damage

State Update Action, including their dependency on

an event type or BOM to carry out the pattern action,

maybe provided elsewhere in the BOM using the

pattern of interplay template component.

Table 5. State machine for target entity.

4.2.2. Activity Diagram

We use Poseidon for UML PE 5.0.1 for the

modeling of state machine for Target Entity as mention

in section 4.2.1.

Figure 2. Weapons effect BOM using UMLActivity Diagram.

Each block identifies a sate, and the message lines

between states represent the pattern action that takes

place, thereby satisfying that exit condition.

4.2.3. Transformation

After Activity modeling we extract metadata in

form of XMI from Poseidon, then send this XML as

input into XSLT Processor parallel with XSLT

Mapping rules. The output of XSLT processor [28]

will be an OWL file which contains output ontology.

The output ontology can be viewed at [24] because of

the space limitations.

5. Conclusion and Future work

In this paper, we proposed a solution to problemsof representing behavioral knowledge expressed in

UML activity diagram as OWL ontology. According to

our proposed method, a UML activity diagram is

modeled in a UML modeling tool. An XMI is exported

from the tool, which encloses the behavioral

knowledge expressed in a particular UML activity

diagram. The XMI is the input to XSLT Processor. On

the other hand we have designed target process

ontology expressed in OWL. This ontology is specially

modeled to match the needs of our research.

The mapping rules are script in form of XML Style

sheet Language Transformation XSLT is used to script

the mapping rules in the form of XML. XSLT together

with XMI representation of UML activity diagram is

used as input to the XSLT Processor. The output is

OWL ontology expressing the behavior knowledge

represented by activity diagram.

In future we shall work on other frequently used

process models like Petri Nets, UML Sequence

Diagram and BPMN (Business Process ModelingNotation).

6. References

[1] Process Modeling Definition. Available from:http://www.cbu.edu/~lschmitt/I351/glossary.htm

[2] Petri Nets. Information available from:http://www.petrinets.info/

[3] Braun et al. UML Activity model. Available from:

http://atlas.kennesaw.edu/~dbraun/csis4650/A&D/UML_tutorial/activity.htm

[4] Donald Bell. UML Sequence Diagram. Available

from:http://www.ibm.com/developerworks/rational/library/3101.html

[5] Object Management Group (OMG). Business ProcessModelling Notation. Available from:

http://www.bpmn.org/[6] T. R. Gruber, 1993, A translation approach to portable

ontologies.KnowledgeAcquisition, 5(2), pp. 199-220.

http://portal.acm.org/citation.cfm?id=173747

[7] Stanislav Ustymenko, 2005, Ontology-SupportedSharing and Reuse of Knowledge in Diverse

Environments, in Proceedings of the 43rd annual

StateMachine

Name

ConceptualEntity

StateNote

State Name Exit Condition

Exit Action Next State

Target

States

Target

Entity

Ready Weapon Fire Action Under Fire Na

Under Fire Munition DetonationAction

ImpactDetonation

Na

ImpactDetonation

Damage State UpdateAction

Ready Na


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Southeast regional conference - Volume 2, pp. 347-348, Kennesaw, Georgia.

[8] W3C Consortium. Web Ontology Language (OWL).Available from: http://www.w3.org/2004/OWL/

[9] Stephen Cranefield. UML and the Semantic Web.In

proceedings of the International Semantic WebWorking Symposium (SWWS), pages 113-130, 2001.

[10] Baclawski et al. Extending UML to support ontology

engineering for the semantic web in the bookUML2001 The Unified Modeling Language. Modeling

Languages, Concepts, and Tools, pages 342-360.

[11] Kabilan, V., Johanneson, P., UML for ontology

modeling and interoperability. Proceeeding of 1st INTEROP-EMOI Open Workshop on EnterpriseModels and Ontologies for Interoperability, Co

Located with CAiSE, 2004.

[12] Falkovych et al, 2002, UML for the Semantic Web:

Transformation-based Approaches. Available from:http://www.cwi.nl/~media/publications/UML_for_SW.

pdf.

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[14] Grnmo, R. et al. Transformations between UML andOWL-S,Proceedings of the 1st European Conferenceon Model Driven Architecture: Foundations and

Applications, Nuremberg, Germany, pages 269-283,2005.

[15] S. Cranefield and M. Purvis, UML as an ontologymodeling language. Proceedings of the Workshop on

Intelligent Information Integration, 16th International

Joint Conference on Artificial Intelligence (IJCAI-99),1999.

[16] H. Na, O. Choi, J. Lim, A Method for Building

Domain Ontologies based on the Transformation ofUML Models, Fourth International Conference onSoftware Engineering Research, Management and

Applications (SERA'06) pp. 332-338, 2006.

[17] W3C Consortium. XML Style sheet LanguageTransformation. Available from:http://www.w3.org/TR/xslt

[18] Jenz & Partner. Open Source Business Management

Ontology (BMO). Available from:http://www.bpiresearch.com/Resources/RE_OSSOnt/re

_ossont.htm

[19] The GO Consortium. Biological Process Ontology.

Available from:http://www.geneontology.org/GO.process.guidelines.shtml

[20] Wongthongtham et al. Software design processontology development in Meersman, R. and Tari, Z.and Herrero, P. (ed), 2nd IFIP WG 2.12 & WG 12.4

International Workshop on Web Semantics (SWWS) inconjunction with OTM 2006, pages 1806-1813,

Montpellier, France, Oct 29 2006. Springer-Verlag,USA.

[21] The GO Consortium. Gene Ontology. Availablefrom: http://www.geneontology.org/

[22] Aitken et al. A Process Ontology. Springer Berlin /Heidelberg, ISBN: 978-3-540-44268-4, pages 263-270,Date: January 01, 2002.

[23] D. Martin et al. OWL-S: Semantic Markup for WebServices. Available from:http://www.daml.org/services/owl-s/1.1/overview/

[24] UAD-OWL target ontology figure. Informationavailable from:http://users.utu.fi/moania/Innovation08/

[25] Protg. http://protege.stanford.edu/

[26] Kim et al., Describing Semantic Web Services: FromUML to OWL-S. ICWS 2007. IEEE International

Conference on Web Services. 9-13 July 2007, pp 529-536, 2007.

[27] SISO Based Object Model product development group.Base Object Model (BOM) Template Specification.

Available from:

www.boms.info/spec/BOM_Specification_v2006_FINAL.pdf

[28] XSLT Processor XALANhttp://xml.apache.org/xalan-j/

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