Web Ontology Language for Web Services

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The Web Ontology Language for Web Services (OWL-S for short), formerly DAML-S, is a specification for the semantic labeling of web services . OWL-S relies heavily on extensions: OWL-S specifies ontologies in order to semantically describe a service on a technical level - however, in order to semantically clarify the subject-specific functionality of a service, an additional ontology is always necessary that covers the corresponding subject domain.

For example, to describe a service for the sale of books, ontologies going beyond OWL-S are necessary to describe transactions for the sale and to describe books. OWL-S itself only offers the ontologies for describing the necessary description of preconditions for service execution, the input and output data and the side effects of the service.

Contrary to what the name suggests, OWL-S is not an extension of OWL , i. i.e. no new language elements are defined. OWL-S is a domain-specific language specified by OWL for the description of web services.

Objectives of OWL-S

OWL-S should

  • automatic web service discovery,
  • automatic web service invocation (execute),
  • automatic web service composition and interoperation and
  • automatic web service monitoring (monitoring)

enable.

Structure of OWL-S

OWL-S is based on the following three questions:

  • What is the service doing? (Service Profile)
  • How is this done? (Service model)
  • How is the service applied? (Service grounding)

Service Profile

The service profile is primarily used for service discovery and contains information about the organization that offers the service, the preconditions, input and output values, as well as properties and benefits of the service (IOPEs - inputs, outputs, preconditions and effects). To put it casually, the service profile is an advertisement for the service. Once the service has been selected for use (i.e. after service discovery) the service profile is no longer needed. Rather, the service description contained in the service model is used to use the service.

Service model

The service model is used to actually execute the service and describes it as a process. A distinction is made between atomic and composite processes, as well as simple (abstract and non-executable) processes. The service model (also called process model) describes how a client can use the service. It describes the input and output data, preconditions and effects (IOPEs) of individual services. These can differ greatly from the IOPEs that are described in the Service Profile. In theory, you can even describe a completely different service. However, this would be useful neither for the service provider nor for the user.

Service grounding

The service grounding includes protocol, format and addressing details and therefore provides information for realizing the more abstract information of the other levels. Here WSDL used. The grounding represents a kind of mapping between the service model and the technical execution level, i. h., z. B. The service model translates input and output messages into corresponding WSDL elements. In principle, other groundings are also conceivable that are not based on WSDL. Due to the widespread use and acceptance of WSDL, WSDL grounding is the only one that is specifically described in the W3C submission.

See also

Web links