=Paper=
{{Paper
|id=None
|storemode=property
|title=A Graphical Tool for Automatic Generation of OWL Ontologies
|pdfUrl=https://ceur-ws.org/Vol-942/paper_3.pdf
|volume=Vol-942
}}
==A Graphical Tool for Automatic Generation of OWL Ontologies ==
https://ceur-ws.org/Vol-942/paper_3.pdf
A Graphical Tool for Automatic Generation of OWL
Ontologies
Aissam BELGHIAT Mustapha BOURAHLA
Department of Computer Science Department of Computer Science
University of Md Boudiaf, Msila, 28000, Algeria University of Md Boudiaf, Msila, 28000, Algeria
Belghiatissam@gmail.com mbourahla@hotmail.com
Abstract—The ontologies are became the backbone of the generated tool to OWL ontologies represented in RDF/XML
semantic web, the development of these ontologies from scratch is format.
a very difficult task. The use of models is useful to deal with such The rest of the paper is organized as follows: In Section 2,
problems since it allows visually modeling of the ontologies we present some related works. In Section 3, we present some
themselves. In this paper, we propose an approach based on the
combined use of Meta-modeling and Graph Grammars to
basic notions about UML, OWL. In Section 4, we present
automatically generate a visual modeling tool for OWL concepts about model and graph transformation, and then we
ontologies. In our approach registered in the MDA architecture, give an overview of the AToM3 tool [1]. In Section 5, we
the UML Class diagram formalism is used to define a meta- describe our approach that provides a graphical environment
model of class diagrams. The meta-modeling tool ATOM3 is used for automatic generation of OWL ontologies. In Section 6, we
to generate a visual modeling tool according to the proposed class illustrate our tool through an example. Finally concluding
diagram meta-model. We have also proposed a graph grammar remarks drawn from the work and perspectives for further
to automatically generate OWL ontologies of the graphically research are presented in Section 7.
specified class diagram models. This allows the user to pass a
very important step in the development process of OWL II. RELATED WORKS
ontologies. Our environment is illustrated through an example.
The idea of our work is not innovating, indeed several
Index Terms—UML, Ontology, OWL, ATOM3, MDA. works exist in the literature tackle this subject. In [14] the
authors proposed a transformation of UML towards DAML at
I. INTRODUCTION the end of the Nineties, by showing similarities and differences
between the two languages. In [15] the work of “Converting
The ontologies are became the backbone of the semantic UML to OWL Ontologies” proposed a transformation of
web, this last provides various languages for representing Ontology UML Profile (OUP) towards an ontology OWL. In
ontologies including XML, RDF, DAML, and OWL. OWL [6] the OMG notices the interest of such subject and proposed
(Ontology Web Language) is the most widely used of these in its turn the ODM which provides a profile for writing RDF
languages because of its high expressive power and the fact and OWL within UML, it also includes partial mappings
that it is the W3C standard ontology language for the Semantic between UML and OWL as well as mappings amongst RDF,
Web [10]. RDFS, Common Logic and Topic Maps, it should be noted that
In the other hand, UML is the unified object oriented several works are carried out like answer to the call of the
modeling language which became an important standard OMG and gathered in the ODM that we do not evoke here. In
widely used by domain experts for expressing their domain [9], the author presented an implementation of the ODM using
knowledge. The development of OWL ontologies from scratch ATL language. In [5], the author used a style sheet
is a very difficult task. The use of models is useful to deal with “OWLfromUML.xsl” applied to an XMI file (intermediate
such problems since it allows visually modeling of the format of UML model) to generate an ontology OWL DL
ontologies themselves. An OWL ontology visualized as UML represented as RDF/XML format. And finally in [16], the
diagrams allow us to better describe our ontology to humans, authors proposed a detailed comparison between UML and
and most people can understand an UML class diagram at a OWL that carried out in 2008. In the other side Atom3 has
glance. In this paper we propose an approach based on the been proven to be a very powerful tool allowing the meta-
combined use of Meta-modeling and Graph Grammars to modeling and the transformations between formalisms, in [1]
automatically generate a visual modeling tool for OWL and other works we can found treatment of class diagrams,
ontologies. We implement these concepts presented above in activity, and other UML diagrams. In these works the Meta
ATOM3: A Tool for Multi-formalism and Meta-Modeling [1]. modeling allows visual modeling and graph grammar allows
We propose an UML class diagram meta-model and we use the the transformation.
meta-modeling tool AToM3 to generate automatically a visual Obviously, the heart of our work is articulated on
modeling tool to process UML class diagram models. We also transformation rules and their implementation. In pre-ceding
define a graph grammar to translate the models created in the
works, the transformation rules are more specific and reflect a
general opinion of the author often related to a specific field
which he works on (specific transformation). In this paper we
propose another vision different from that approached in
preceding works either in the proposition of transformation
rules, or in theirs implementation, this vision is to propose the
transformation rules in a level of abstraction close to the
application in order to obtain usable ontologies, because more
the selected level of abstraction is close to the application
minus ontology is reusable, but more it is usable. Then we
propose a graph grammar implementation for these rules. Fig. 1. Model transformation principle.
III. OWL FROM UML CLASS DIAGRAM Graph transformation was largely used for the expression
UML (Unified Modeling Language) is a language to of model transformation [4]. Particularly transformations of
visualize, specify, build and document all the aspects and visual models can be naturally formulated by graph
artifacts of a software system [7]. UML defines thirteen transformation, since the graphs are well adapted to describe
diagrams; some of them represent the system statically while the fundamental structures of models.
others show the functionalism of the system. The class diagram The set of graph transformation rules constitutes what is
is considered very important for object oriented modeling; it called the model of graph grammar; each rule of a graph
shows the internal structure of a system and makes it possible grammar is composed of a left hand side (LHS) pattern and of
to provide an abstract representation of its objects [2]. a right-hand sided (RHS) pattern.
OWL (Ontology Web Language), was recommended by the Therefore, the graph transformation is the process to choose
W3C in 2004, and its version 2 in 2009, is designed for use by a rule among the graph grammar rules, apply this rule on a
applications that need to process the content of information graph pattern that is matched with the LHS pattern to produce
instead of just presenting information to humans. OWL1 offers the RHS pattern, and reiterate the process until no rule can be
three sub-languages with increasing expression intended for applied [4].
specific communities of developers and users: OWL Lite,
OWL DL, and OWL Full [10] whereas OWL2 defines three
new profiles: OWL2 EL, OWL2 QL, and OWL2 RL [13]. B. AToM3
UML and OWL have different goals and approaches; AToM3 [1] “A Tool for Multi-formalism and Meta-
however they have some overlaps and similarities, especially Modeling” is a visual tool for model transformation, written in
for representation of structure (class dia-grams). UML and Python [8] and is carried out on various platforms (Windows,
OWL comprise some components which are similar in several Linux, …). It implements various concepts like multi-paradigm
regards, like: classes, associations, properties, packages, types, modeling, meta-modeling and graph grammars. It can be also
generalization and instances [6]. UML is a notation for used for simulation and code generation.
modeling the artifacts of objects oriented software, whereas AToM3 provides visual models those are conform to a
OWL is a notation for knowledge representation, but both are specific formalism, and uses the graph grammar to go from a
modeling languages. model to another.
In the next sections, we will discuss how we use AToM3 to
meta-model class diagrams and how to generate OWL models
IV. GRAPH TRANSFORMATION by applying a graph grammar.
A. Overview V. OUR APPROACH
Modeling and model transformation play an essential role Our solution is implemented in AToM3. Our choice is
in the MDA “Model Driven Architecture”. MDA recommends quickly related to AToM3 because of the advantages which it
the massive use of models in order to allow a flexible and presents like its simplicity, and its availability. In our approach
iterative development, thanks to refinements and enrichments we have to profit from the convergence between UML and
by successive transformations. OWL especially for representation of structure (class
A model transformation is a set of rules that allows passing diagrams), most people can model and understand UML class
from a meta-model to another, by defining for each one of diagram at a glance, it is not the case in different
elements of the source their equivalents among the elements of representations of ontologies like RDF/XML, Turtle or other
the target. These rules are carried out by a transformation representations. We have to benefit of visualizing OWL
engine; this last reads the source model which must be conform ontologies as UML class diagram models.
to the source meta-model, and applies the rules defined in the For the realization of this application we have to propose
model transformation to lead to the target model which will be and to develop a meta-model of class diagram (figure 2), this
itself conform to the target meta-model. The principle of model meta-model allows us to edit visually and with simplicity class
transformation is illustrated by figure 1: diagrams on AToM3 canvas. In addition to meta-model
proposed we develop a graph grammar made up of several Association class
rules which allows transforming progressively all what is An association-class is transformed to OWL class (implementation level),
modeled on the canvas towards an OWL ontology stored in a named (ac-ssociationclassname). The latter is connected to the left part by a
relation named (AG_AC-associationclassname), and to the right part by a
disk file (fig.2). The graph grammar is based on transformation relation named (AD_AC-associationclassname). We named also the two new
rules; those rules try to transform the class diagram in the roles on the two new association ends (RG_AC- associationclassname) and
(RD_AC- associationclassname). After these transformations on the
implementation level, always in order to obtain at the end association class we find ourselves on the situation of transformation of
usable ontologies. binary associations (which is treated previously).
For the ontology, the choice among OWL profiles is made
on OWL DL because it places certain constraints on the use of B. Datatypes transformation
the structures of OWL such as separation two to two between UML data types are transformed into XML schema (XSD)
classes, datatypes, datatype properties, objects properties, data types because OWL uses the majority of the datatypes
annotation properties, ontologies properties, individuals, data integrated into XML schema. The calls of these datatypes are
values, and integrated vocabulary [11]. That means, for done through datatype URI address reference
example, a class cannot be at the same time an individual [12]. http://www.w3.org/2001/XMLSchema [11]. The instances of
These constraints enable us to lead to our objective which is an the primitive types used in UML itself include: Boolean,
ontology well reflecting what is modeled in a class diagram. Integer, String, and UnlimitedNatural [7]. Table II presents the
UML primitive datatypes and their transformations.
TABLE II. DATATYPES TRANSFORMATION.
UML XSD
Integer xsd:integer
Boolean xsd:boolean
String xsd:string
xsd:nonNegativeInteger
UnlimitedNatural
xsd:positiveInteger
C. Meta-model of UML Class diagram
To build UML class diagram models in AToM3, we have
to define a meta-model for them. Our meta-model is composed
Fig. 2. Transformation sequence. of two classes and four associations developed by the meta-
formalism (CD_classDiagramsV3), and the constraints are
expressed in Python [8] code (fig. 3):
A. Transformation rules
Our approach is realized according to suggested
transformation rules (Table I). We propose a set of rules in
particular for classes‟ transformation, enumerations,
associations, roles, dependencies, association classes, and
almost all the elements of a class diagram. The level of
abstraction in those rules is close to the application in order to
have usable ontologies. For lack of space, we have presented
some of these rules.
TABLE I. UML TO OWL TRANSFORMATION RULES.
Class
An UML class is transformed to an OWL class; the name of the class is
preserved.
Fig. 3. Class diagram meta-model.
Inheritance
The specialized class is defined subclass of the generalized class. After we built our meta-model, it remains only its
Class Attributes generation. The generated meta-model comprises the set of
An attribute is transformed into a property, and the transformation is carried
classes modeled in the form of buttons which are ready to be
out according to the type of attribute. If the type of the attribute is a primitive employed for a possible modeling of a class diagram.
type, the attribute is transformed into datatype property. If the value of the
attribute is a class, it is transformed into object property. D. The Proposed Graph grammar
To perform the transformation between class diagrams and
Bidirectional association
OWL ontologies, we have proposed a graph grammar
Associations are transformed into object properties. An inverse object
property is generated automatically named (Inverse-associationname). composed of an initial action, ten rules, and a final action. For
lack of space, we have not presented all the rules.
Initial Action: Ontology header TABLE IV. GENERALIZATION TRANSFORMATION.
Role: In the initial action of the graph grammar, we created a Condition
file with sequential access in order to store generated OWL
code. Then we begin by writing the ontology header which is
fixed for all our generated ontologies (fig. 4).
:=
Action
Fig. 4. Ontology header definition.
Rule 1: Class transformation
Name: class2class
Priority: 1
Rule 3: Binary association transformation
Role: This rule transforms an UML class towards an OWL
Name: asso2prop
class (see Table III). In the condition of the rule we test if the
Priority: 3
class is already transformed, if not, in the action of the rule we
Role: This rule transform an association of the class diagram
reopen the OWL file to add the OWL code of this class.
towards an OWL object property, it allows also the
TABLE III. CLASS TRANSFORMATION. transformation of roles and cardinalities of this association.
Condition TABLE V. ASSOCIATION TRANSFORMATION.
Condition
:=
Action
:=
Action
Rule 2: Generalization transformation
Name: gener2sclass
Priority: 2
Role: This rule transforms a generalization by indicating that
the specialized class is defined as sub-class of the generalized
class (Table IV).
Rule 4: Association-class transformation
Name: ac2class
Priority: 1
Role: This rule allows the promotion of association class to a
full class (see Table VI), that reflects what we show in the
transformation rules. This class takes as name the name of the
LHS class-association preceded by (AC-). Two binary
associations are created in the RHS named AG_AC, AD_AC,
thus two new roles RG_AC and RD_AC as illustrated in the
transformation rules.
TABLE VI. ASSOCIATION-CLASS TRANSFORMATION.
Condition
No condition. Fig. 6. Class diagram of our ontology.
We start the execution of our graph grammar; we obtain the
intermediate graph (see fig. 7). In parallel, there is an automatic
generation of the file which contains OWL code stored on hard
:= disc (see fig. 9):
Action
No action
Final Action: Definition of the end of ontology
Role: In the final action of the graph grammar, we end our
ontology, we will have to open our file and to add
„‟ (see fig. 5).
Fig. 7. Intermediate graph.
After the execution of the graph grammar on our example
we obtain our ontology generated and stored. We can visualize
this ontology by specialized tools such as SWOOP (fig. 8):
Fig. 5. End of ontology.
VI. EXAMPLE
Let us apply our approach on a simple example of
development of a small OWL ontology which describes a
population; it describes a group of people and their relations of
parenting.
The population which we wish to describe is made up of
humans, and divided into two subclasses Man and Woman. Fig. 8. Ontology Visualisation by SWOOP.
Human can have a relationship with another human. A man
and a woman can be married. This small ontology can be Figure 9 presents the source RDF/XML of our generated
modeled quite simply with the class diagram (fig. 6). ontology.
VII. CONCLUSION
We saw in this paper how to implement an application
which makes a graphical environment for the automatic
generation of OWL ontologies based on class diagram models
and by using graph transformation in particular the powerful
tool AToM3. For the realization of this application we
developed a meta-model for UML class diagrams, and a graph
grammar composed of several rules which enables us to
transform all what is modeled visually in our AToM3
generated environment to an OWL ontology stored in a hard
disk file.
In future work, we plan to extend the environment to
automatically generate OWL/SWRL from UML/OCL models
in AToM3.
REFERENCES
[1] AToM3. Home page: http://atom3.cs.mcgill.ca.2002.
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Model-Driven Architecture”, Lecture Notes in Computer
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[5] Sebastian Leinhos, http://diplom.ooyoo.de, 2006.
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[10] W3C OWL Working Group, “OWL Web Ontology Language-
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20040210/. Recommendation 10 Feb 2004.
[11] W3C OWL Working Group, “OWL Web Ontology Language–
Guide”, http://www.w3.org/TR/2004/REC-owl-guide-
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Reference”,http://www.w3.org/TR/2004/rec-owl-ref-20040210.
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[13] W3C OWL Working Group, “OWL 2 Web Ontology Language
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overview-20091027.W3C Recommendation 27 October 2009.
[14] Kenneth Baclawski2 and all “Extending UML to Support
Ontology Engineering for the Semantic Web”.
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Damjanović “Converting UML to OWL Ontologies”, 2004.
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and OWL”,2008.
Fig. 9. Generated OWL ontology.