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2 Using Ontologies
Ontology technologies are frequently applied to many subject domains nowadays
[ 3, 21] . As mentioned in [ 9] , we consider an ontology as a thesaurus of words and
inference rules on it, where the words in the thesaurus represent concepts and the
inference rules operate on the relationships on the words. Each concept of an ontol-
ogy can be considered as a semantic atomic element that has a unique meaning in a
subject domain [ 14] . That is to say, the thesaurus part of the ontology plays a role
of a semantic domain in denotational semantics as mentioned in Sect. 1, and the
inference rules help semantic processing by computer [ 6] .
Below, let's consider how a requirements analyst uses an ontology of a subject
domain for completing a sequence diagram. During drawing the sequence diagram,
the analyst should map its elements into atomic concepts of the ontology as shown
in Fig. 2. In the figure, the ontology of a subject domain is written in the form of
class diagrams. For example, the message “aaa” in the sequence diagram is mapped
into the concepts A and B. Formally, the analyst specifies a semantic mapping F
where F (aaa)
{A, B}. According to the notation of web contents, we can use
the semantic tags which have the same names as the mapped concepts and write
this semantic mapping like <A><B>aaa</B></A> in the sequence diagram. The
sequence diagram may be incrementally improved, and logical inference on the
ontology suggests to the analyst which parts she or he should incrementally improve
or refine. In the figure, although the sequence diagram includes the concept A at the
item “aaa”, it does not have the concept C, which is caused by A. The inference
resulted from “C is caused by A” and “A is included” suggests to the analyst that a
diagram element having C, e.g. a message “ccc” should be added to the sequence
diagram. Note that a meta model of sequence diagrams can define their abstract syn-
tax and we can check any sequence diagram using the meta model. However, this
check is on syntactical aspects only.
Figure 3 illustrates a semantic mapping of the lift control system shown in Fig. 1.
Since we check the semantic aspect of the sequence diagram specifying a lift control
system, we use an ontology of lift-control domain as shown in the right part of the
=
Artifact
aaa
ccc
bbb
semantic mapping
A
B
E
cause
C
C
D
Fig. 2 Basic idea: semantic
mapping
Ontology (thesaurus part only)
 
 
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