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Semantic Web Services 179
atomic process, a grounding that enables the requester to construct input and output
messages must be provided.
– Simple process: is not executable and is not associated with grounding, but like atomic
process, it is executed in one step. It can be used as an element of abstraction of an
atomic process using the realizedBy property or as a simplified representation of
a composite process using the expandsTo property.
– Composite process: is decomposable into other non-composite or composite processes.
The decomposition is specified using the control constructs by a composedBy property:
SEQUENCE, IF-THEN-ELSE, REPEAT-UNTIL and others. Each control construct
is associated with a property called components to indicate the ordering and the
conditional execution of the sub-processes.
An XML fragment of OWL-S ontology describing composite process of airline ticked booking
is presented below 4 .
This is the top level process for BravoAir
6.2.3 WSMO
WSMO [70] provides ontological specifications for the core elements of Semantic Web Services.
It has its conceptual basis in the Web Service Modeling Framework (WSMF). WSMO
is meant to be a meta-model for Semantic web service related aspects. It uses the MOF (Meta
Object Facility) [62] to define such a model. The MOF metadata architecture defines four
layers for models, see Figure 6-10:
– information layer is comprised of data we want to describe.
– model layer is comprised of the metadata that describes data in the information layer.
– the metamodel layer is comprised of the descriptions (i.e., meta-metadata) that define
the structure and semantics of metadata.
– The meta-metamodel layer is comprised of the description of the structure and semantics
of meta-metadata.
4 Retrieved from http://www.daml.org/services/owl-s/1.0/examples.html