hy-566 internet knowledge management owl-s: semantic markup for web services baryannis george, met...
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HY-566 Internet Knowledge Management
OWL-S: Semantic Markup for Web Services
Baryannis George, METTesseris George, MET
HY-566 Internet Knowledge Management
OWL-S Stands for Web Ontology Language for Services An OWL ontology/language to formally describe Web
services Began as part of the DARPA DAML project, formerly known as
DAML-S Currently in version 1.1 / 1.2 Prerelease
WSDL supports only syntactic web service descriptions Only syntactic support for discovery, invocation and
composition Web Service usage and integration needs to be supported
manually
OWL-S provides a semantic layer for web service description using ontologies Ontologies provide machine-understandable semantics Semantics deals with meaning/content More effective web service discovery, invocation, composition
and interoperation
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OWL-S Upper Ontology
Capabilities description Service requirements Quality of Service Classification in Service
taxonomies
Control flow of the service Service viewed as a process Data Flow Parameter bindings
Mapping from abstract to concrete (e.g. OWL-S to WSDL)
Inputs/Outputs to Messages Atomic processes to
operations
Cardinality constraints Service described by at most one ServiceModel ServiceGrounding associated by exactly one Service
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Service Profile
Service Profile Provider information
contact information Functional description
inputs and outputs preconditions and effects
Service features Category and QoS Unbounded list of parameters (max
response time, geographic availability etc.)
Two main uses: Advertisement of Web Services
capabilities (non-functional properties, QoS, Description, classification, etc.)
Request of Web services with a given set of capabilities
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Service Model
Service Model Describes how a service works: internal
processes of the service in addition to inputs, outputs, preconditions and results
Three types of processes: Atomic: single interaction, directly
invokable Composite: decomposable into other
processes (composite or not) Simple: either abstract views of atomic
processes or simplified views of composite processes
Defines the control structure of composite processes
Sequence, Split, Split+Join, Any-Order, Choice, If-Then-Else, Iterate, Repeat-While, Repeat-Until
Facilitates Web service invocation Composition of Web services Monitoring of interaction
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Service Grounding
Service Grounding Specifies how to access the service
(protocol and message formats, serialization, transport and addressing)
Service Model + Grounding give everything needed for using the service
One possible grounding approach is to build upon WSDL to define message structure and physical binding layer
WsdlGrounding subclass that maps to specific elements in the WSDL specification such as operations, ports and messages
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Service Profile In Detail (1/6)
serviceName A name for the service that
can be used as an identifier textDescription
A brief description of the service (what the service offers, what it requires etc.)
contactInformation provides a mechanism of
referring to individuals responsible for the service. The range of this property is unspecified within OWL-S, but can be restricted to some other ontology (e.g. Actor class)
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Service Profile In Detail (2/6)
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Service Profile In Detail (3/6)
hasParameter ranges over a Parameter instance of the Process ontology. Inputs and
Outputs are kinds of Parameters hasInput
specifies one of the inputs of the service hasOutput
specifies one of the outputs of the service hasPrecondition
specifies one of the preconditions of the service
hasResult specifies one of the results of the service. It specifies under what conditions the outputs are generated (postconditions). Also, the Result specifies what domain changes are produced during the execution of the service. (effects)
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Service Profile In Detail (4/6)
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Service Profile In Detail (5/6)
serviceParameter an expandable list of properties, instances of
the class ServiceParameter. serviceParameterName: the name of the
actual parameter sParameter: points to the value of the
parameter within some OWL ontology. serviceCategory
refers to an entry in some ontology or taxonomy of services. Instance of the class ServiceCategory
categoryName: the name of the actual category
taxonomy: a reference to the taxonomy scheme.
value: points to the value in a specific taxonomy
code: code associated to a taxonomy. serviceClassification
defines a mapping from a Profile to an OWL ontology of services (NAICS specification)
serviceProduct defines a mapping from a Profile to an OWL
ontology of products (UNSPSC specification)
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Service Profile In Detail (6/6)
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Why OWL instead of RDFS The goal behind OWL-S is for web sites to be able to employ
a standard ontology for declaring and describing services The authors state that “the ontology structuring
mechanisms of OWL provide an appropriate, Web-compatible representation language framework” that allows them to achieve their goal
Some OWL characteristics that were necessary for OWL-S are: Cardinality constraints Classes expressions involving unionOf, disjointUnionOf,
intersectionOf, or complementOf Inference: constructs such as inverseOf, and disjointWith are
used in the declaration of properties
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References OWL-S: Semantic Markup for Web Services v1.1,
David Martin et al., 2004 http://www.daml.org/services/owl-s/1.1/
OWL-S: Semantic Markup for Web Services v1.2 Prerelease, David Martin et al., 2006 http://www.ai.sri.com/daml/services/owl-s/1.2/
Web Service Description Languages, Presentation and report, George Tesseris
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