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Typus
KomplettPlagiat
Bearbeiter
Graf Isolan
Gesichtet
Yes.png
Untersuchte Arbeit:
Seite: 21, Zeilen: 3-42
Quelle: Cabral et al 2004
Seite(n): 234-235, Zeilen: 234:3ff - 235:1ff
OWL-S

OWL-S [49] is an upper ontology used to describe the semantics of services based on the W3C standard ontology OWL and is grounded in WSDL. Its approach originated from an Artificial Intelligence background and has previously been used to describe agent functionality within several multi-agent systems as well as with a variety of planners to solve higher level goals. It consists of three main upper ontologies: the Profile, Process Model and Grounding.

The Profile is used to describe services for the purposes of discovery; service descriptions and queries are constructed from a description of functional properties (i.e. inputs, outputs, preconditions, and effects - IOPEs), and non-functional properties (human oriented properties such as service name, etc, and parameters for defining additional meta data about the service itself, such as concept type or quality of service). In addition, the profile class can be sub-classed and specialized, thus supporting the creation of profile taxonomies which subsequently describe different classes of services.

The Process Models describe the composition or orchestration of one or more services in terms of their constituent processes. This is used both for reasoning about possible compositions (such as validating a possible composition, determining if a model is executable given a specific context, etc) and controlling the enactment/invocation of a service. Three process classes have been defined: the composite, simple and atomic process. The atomic process is a single, black-box process description with exposed IOPEs. Inputs and Outputs relate to data channels, where data flows between processes. The preconditions specify facts of the world that must be asserted in order for an agent to execute a service. Effects characterize the facts that become asserted given a successful execution of the service, such as the physical side-effects that the execution the service has on the physical world. The simple process provides a means of describing service or process abstractions, which means that such elements have no specific binding to a physical service, and thus have to be realized by an atomic process (e.g. through service discovery and dynamic binding at run-time), or expanded into a composite process. The composite processes are hierarchically defined work-flows, consisting of atomic, simple and other composite processes. These process work-flows are constructed using a number of different composition constructs, including: Sequence; Unordered; Choice; If 􀀀 then 􀀀 else; Iterate; Repeat 􀀀 until; Repeat 􀀀 while; Split, and Split + join. The profile and process models provide semantic frameworks whereby services can be discovered and invoked, based upon conceptual descriptions defined within Semantic Web (i.e. OWL) ontologies.

The Grounding provides a pragmatic binding between this concept space and the physical data/machine/port space, thus facilitating service execution. The process model is mapped to a WSDL description of the service, through a thin grounding. Each atomic process is mapped to a WSDL operation, and the OWL-S properties used to represent inputs and outputs are grounded in terms of XML data types. Additional properties pertaining to the binding of the service are also provided (i.e. the IP address of the machine hosting the service, and the ports used to expose the service).


[49] OWL-S Semantic Markup for Web Services; http://www.w3.org/Submission/OWL-S/

[Seite 234]

6 OWL-S approach

OWL-S (previously DAML-S [9]) consists of a set of ontologies designed for describing and reasoning over service descriptions. OWL-S approach originated from an AI background and has previously been used to describe agent functionality within several Multi-Agent Systems as well as with a variety of planners to solve higher level goals.

OWL-S combines the expressivity of description logics (in this case OWL) and the pragmatism found in the emerging Web Services Standards, to describe services that can be expressed semantically, and yet grounded within a well defined data typing formalism. It consists of three main upper ontologies: the Profile, Process Model and Grounding. The Profile is used to describe services for the purposes of discovery; service descriptions (and queries) are constructed from a description of functional properties (i.e. inputs, outputs, preconditions, and effects - IOPEs), and non-functional properties (human oriented properties such as service name, etc, and parameters for defining additional meta data about the service itself, such as concept type or quality of service). In addition, the profile class can be subclassed and specialized, thus supporting the creation of profile taxonomies which subsequently describe different classes of services.

OWL-S process models describe the composition or orchestration of one or more services in terms of their constituent processes. This is used both for reasoning about possible compositions (such as validating a possible composition, determining if a model is executable given a specific context, etc) and controlling the enactment/invocation of a service. Three process classes have been defined: the composite, simple and atomic process. The atomic process is a single, black-box process description with exposed IOPEs. Inputs and outputs relate to data channels, where data flows between processes. Preconditions specify facts of the world that must be asserted in order for an agent to execute a service. Effects characterize facts that become asserted given a successful execution of the service, such as the physical side-effects that the execution the service has on the physical world. Simple processes provide a means of describing service or process abstractions – such elements have no specific binding to a physical service, and thus have to be realized by an atomic process (e.g. through service discovery and dynamic binding at run-time), or expanded into a composite process. Composite processes are hierarchically defined workflows, consisting of atomic, simple and other composite processes. These process workflows are constructed using a number of different composition constructs, including: Sequence, Unordered, Choice, If-then-else, Iterate, Repeat-until, Repeat-while, Split, and Split+join.

The profile and process models provide semantic frameworks whereby services can be discovered and invoked, based upon conceptual descriptions defined within Semantic Web (i.e. OWL) ontologies. The grounding provides a pragmatic binding between this concept space and the physical data/machine/port space, thus facilitating service execution. The process model is mapped to a WSDL description of the ser-

[Seite 235]

vice, through a thin grounding. Each atomic process is mapped to a WSDL operation, and the OWL-S properties used to represent inputs and outputs are grounded in terms of XML data types. Additional properties pertaining to the binding of the service are also provided (i.e. the IP address of the machine hosting the service, and the ports used to expose the service).


8. DAML-S Coalition: DAML-S 0.9 Draft Release. http://www.daml.org/services/damls/0.9/. (2003)

9. Fensel, D., Bussler, C. The Web Service Modeling Framework WSMF. Eletronic Commerce: Research and Applications. Vol. 1. (2002). 113-137

19. OWL-S Coalition: OWL-S 1.0 Release. http://www.daml.org/services/owl-s/1.0/. (2003)

Anmerkungen

Ohne Hinweis auf eine Übernahme.

Sichter
(Graf Isolan), Hindemith

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