A. Web Service Description Language- WSDL
This is well-known standard for describing web service. Basically WSDL contains two sections as:
• Concrete section: This contains list of service endpoints or say ports. Each port has its type declared in abstract section and it’s binding in the concrete section. Bindings are detailed specification for how the operation or functionality of the web service is implemented.
• Abstract section: This contains the abstract definition of the operation using portType tag. Binding in concrete section are derived form portType or interfaces from the abstract section. Operations in portType or Interface contain one or more abstract input definition and one or more output definition. Following figure-1 clarifies structure of WSDL and its two sections, abstract and concrete, with subsections.
B. DBPedia Ontology
It is Cross Domain Ontology. It is designed by combining multiple knowledge resources. When ontology is domain specific it makes it to be used by that domain only and cannot be generalized. DBpedia and OpenCyc are Cross Domain Ontology . Each concept in ontology is described by RDF triplet and relate to other concept using class and sub classes of instances. DBpedia built based on public, open and Wikipedia as a knowledge source. It is being continuously updated and accessible via web service calls. It is free to use it and open for public usage.
C. Semantic Web Service- SAWSDL
It is W3C standard. It stands for Semantic Annotation for Web Service description language and used adding semantic annotations to WSDL standard. SAWSDL provides association between Web service elements in WSDL and Ontology concepts via sawsdl:modelReference extension Attribute. SAWSDL extension attributes has scope up to the description of the abstract section of the web service as concrete section does not required in discovery and composition process. Also extension element does not depend on any specific ontology structure that makes SAWSDL to be language-neutral. Following figure shows SAWSDL annotations in web service.
Apart from sawsdl:modelReference there are other two elements also.
• sawsdl:liftingSchemeMapping: this is for converting XML type to Semantic type.
• sawsdl:LoweringSchemaMapping:this is for converting semantic type to XML type.