Semantic Annotation for Process Models: - Department of Computer ...

68 CHAPTER 4. SEMANTIC ANNOTATION FRAMEWORK
the specific and local process meta-model element. The concepts in a local process
modeling language usually have the is_a relationship with the concepts from a global
process ontology. If the global process ontology can cover all the semantics of the local
modeling language (i.e., the local modeling language is a subset of the global process
meta model ontology), the annotation work can keep the complete semantics of the local
modeling language. If the local process modeling language is more expressive than
the global process ontology (i.e., the set of notations of the local modeling language is
larger than the global one), the model will lose some of the semantics which are not
annotated by the global process ontology. For those lost semantics, referencing the
meta-model of the modeling language is necessary.
A domain ontology provides the standardized terminology and conceptualization of
a particular domain. We suppose that a certain domain ontology is agreed and used to
reconcile the semantics of model contents. The ontological concepts are referenced by
model contents through simple URIs or semantic relationships.
Figure 4.4 provides a depiction of the basic idea of ontology-based semantic annotation.
Process models PM and PN are respectively represented in process modeling
languages M and N. The notations used in process models are instances of modeling
concepts defined in meta-models. For example, the notation for PM1, PM2 and PM4
is an instance of M A , and PN1, PN2 and PN3 are instances of N A . The semantics of
the notations are defined in meta-models. In order to reconcile the semantics of the notations,
a process ontology is used to mediate the mapping between meta-models M and
N. For instance, M A and N A are annotated with a same ontological concept PO x in the
process ontology, which means notations of M A in PM (PM1, PM2 and PM4) stand
for the same meta-model element as notations of N A in PN (PN1, PN2 and PN3).
However, model contents in those notations should also be semantically reconciled to
understand both models, i.e. what domain phenomenon the notations represent. A
domain ontology is referenced to annotate model content. Usually the model contents
represented by the same meta-model element are comparable. For example, the contents
of PM1, PM2 and PM4 should be reconciled with PN1, PN2 and PN3. Since
PM1 and PN1 are annotated with a same domain ontological concept DO x , they are
interpreted as semantically equal concepts when comparing the two models. If the contents
of two model constructs with different meta-model elements reference to a same
domain ontological concept, they are not considered as semantically equal. Although
the contents of PM3 and PN4 have a same ontology reference DO y , they are not same
because they do not share a same modeling ontological concept at the meta level (PO y
for PM3 and PO z for PN4). In this way, various representations of process models are
aligned and reconciled through the reference ontologies, i.e. the process ontology and
domain ontology.
4.2.2 Annotation aspects
Annotation in this work is intended to expose the process knowledge carried by heterogeneous
process models. In general, the annotation should be able to provide both
an overview and a sophisticated comprehension of the process knowledge. We therefore
include a profile annotation to profile process models as products. In the profile
annotation, a set of metadata is defined to describe the significant characteristics of a