OWL-S: Semantic Markup for Web Services Baryannis George, MET Tesseris George, MET HY-566 Internet Knowledge Management

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 HY-566 Internet Knowledge Management

HY-566 Internet Knowledge Management 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 HY-566 Internet Knowledge Management

HY-566 Internet Knowledge Management 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 HY-566 Internet Knowledge Management

HY-566 Internet Knowledge Management 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 HY-566 Internet Knowledge Management

HY-566 Internet Knowledge Management 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 HY-566 Internet Knowledge Management

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) HY-566 Internet Knowledge Management

Service Profile In Detail (2/6) HY-566 Internet Knowledge Management

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) HY-566 Internet Knowledge Management

Service Profile In Detail (4/6) HY-566 Internet Knowledge Management

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) HY-566 Internet Knowledge Management

Service Profile In Detail (6/6) HY-566 Internet Knowledge Management

HY-566 Internet Knowledge Management 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 HY-566 Internet Knowledge Management

HY-566 Internet Knowledge Management 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 HY-566 Internet Knowledge Management