OWL-S: Semantic Markup for Web Services

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OWL-S Semantic Markup for Web Services

• Baryannis George, MET
• Tesseris George, MET

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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

• Mapping from abstract to concrete (e.g. OWL-S to
  WSDL)
• Inputs/Outputs to Messages
• Atomic processes to operations

• Control flow of the service
• Service viewed as a process
• Data Flow
• Parameter bindings

• 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, SplitJoin, 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/serv
  ices/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