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Typus
BauernOpfer
Bearbeiter
Graf Isolan
Gesichtet
Yes.png
Untersuchte Arbeit:
Seite: 20, Zeilen: 7-43
Quelle: Klusch 2008
Seite(n): 43, 44, 45, Zeilen: 43:26-34 - 44:1-25.37-38 - 45:1-2.9ff
SAWSDL

The standard language WSDL for Web Services operates at the mere syntactic level as it lacks any declarative semantics needed to meaningfully represent and reason upon them by means of logical inferencing. In a first response to this problem, the W3C Working Group on Semantic Annotations for WSDL and XML Schema (SAWSDL) [48] developed mechanisms with which semantic annotations can be added to WSDL components.

Unlike OWL or WSML, SAWSDL does not specify a language for representing formal ontologies but provides mechanisms by which ontological concepts that are defined outside WSDL service documents can be referenced to semantically annotate WSDL description elements. Based on its predecessor and W3C member submission WSDL-S [51] in 2005, the key design principles for SAWSDL are that (a) the specification enables semantic annotations of Web Services using and building on the existing extensibility framework of WSDL; (b) it is agnostic to semantic (ontology) representation languages; and (c) it enables semantic annotations for Web Services not only for discovering Web Services but also for invoking them (their grounding).

Based on these design principles, SAWSDL defines the following three new extensibility attributes to WSDL 2.0 elements for their semantic annotation:

• An extension attribute, named modelReference, to specify the association between a WSDL component and a concept in some semantic (domain) model. This modelReference attribute is used to annotate XML Schema complex type definitions, simple type definitions, element declarations, and attribute declarations as well as WSDL interfaces, operations, and faults.

• Two extension attributes, named liftingSchemaMapping and loweringSchema-Mapping, that are added to XML Schema element declarations, complex type definitions and simple type definitions for specifying mappings between semantic data in the domain referenced by modelReference and XML. These mappings can be used during service invocation.

One problem with SAWSDL is that it comes as a mere syntactic extension of WSDL, without any formal semantics. In opposite to OWL-S and (in part) WSML, there is no defined formal grounding of neither the XML-based WSDL service components nor the referenced external metadata sources (via modelReference). Another problem with SAWSDL today is its very limited software support. Notable exceptions are the implemented SAWSDL service discovery and composition planning means of the METEOR-S framework [52]. However, the recent announcement of SAWSDL as a W3C recommendation not only supports a standardized evolution of the W3C Web Service framework in principle (rather than a revolutionary technology switch to far more advanced technologies like OWL-S or WSML) but will push software development in support of SAWSDL and reinforce research on refactoring these frameworks with respect to SAWSDL.


[51] Web Service Semantics (WSDL-S); http://www.w3.org/Submission/WSDL-S/

[52] METEOR-S: Semantic Web Services and Process; http://lsdis.cs.uga.edu/projects/meteor-s/

[Seite 43]

3.3 SAWSDL

The standard language WSDL for Web Services operates at the mere syntactic level as it lacks any declarative semantics needed to meaningfully represent and reason upon them by means of logical inferencing. In a first response to this problem, the W3C Working Group on Semantic Annotations for WSDL and XML Schema (SAWSDL) developed mechanisms with which semantic annotations can be added to WSDL components. The SAWSDL specification became a W3C candidate recommendation on January 26, 20072, and eventually a W3C recommendation on August 28, 2007.

[Seite 44]

3.3.1 Annotating WSDL Components

Unlike OWL-S or WSML, SAWSDL does not specify a new language or toplevel ontology for semantic service description but simply provides mechanisms by which ontological concepts that are defined outside WSDL service documents can be referenced to semantically annotate WSDL description elements. Based on its predecessor and W3C member submission WSDL-S3 in 2005, the key design principles for SAWSDL are that (a) the specification enables semantic annotations of Web Services using and building on the existing extensibility framework of WSDL; (b) it is agnostic to semantic (ontology) representation languages; and (c) it enables semantic annotations for Web Services not only for discovering Web Services but also for invoking them.

Based on these design principles, SAWSDL defines the following three new extensibility attributes to WSDL 2.0 elements for their semantic annotation:

• An extension attribute, named modelReference, to specify the association between a WSDL component and a concept in some semantic (domain) model. This modelReference attribute is used to annotate XML Schema complex type definitions, simple type definitions, element declarations, and attribute declarations as well as WSDL interfaces, operations, and faults. Each modelReference identifies the concept in a semantic model that describes the element to which it is attached.

• Two extension attributes (liftingSchemaMapping and loweringSchema-Mapping) are added to the set of XML Schema element declarations, complex type definitions and simple type definitions. Both allow to specify mappings between semantic data in the domain referenced by modelReference and XML, which can be used during service invocation.

[...]

3.3.2 Limitations

Major critic of SAWSDL is that it comes, as a mere syntactic extension of WSDL, without any formal semantics. In contrast to OWL-S and (in part) WSML, there is

[Seite 45]

no defined formal grounding of neither the XML-based WSDL service components nor the referenced external metadata sources (via modelReference). [...]

Another problem with SAWSDL today is its –apart from the METEOR-S framework by the developers of SAWSDL (WSDL-S) and related ongoing development efforts at IBM– still very limited software support compared to the considerable investments made in research and development of software for more advanced frameworks like OWL-S and WSMO world wide. However, the recent announcement of SAWSDL as a W3C recommendation does not only support a standardized evolution of the W3C Web Service framework in principle (rather than a revolutionary technology switch to far more advanced technologies like OWL-S or WSML) but certainly will push software development in support of SAWSDL and reinforce research on refactoring these frameworks with respect to SAWSDL.

Anmerkungen

Ohne direkten Hinweis auf eine Übernahme.

Auf Seite 20 (Z. 4-6) wird eine von Matthias Klusch verfasste Quelle erwähnt:

"In the following sections, we briefly describe these approaches by taking the text snippets from [43], and refer the reader to this for detailed description.


[43] Matthias Klusch, On Agent-Based Semantic Service Coordination, Cumulative Habilitation Script 2008."

Hier handelt es sich aber um mehr als die Übernahme von "text snippets". Auch ist es fraglich, ob eine so generelle Quellenangabe die nachfolgenden wörtlichen Übernahmen ausreichend kennzeichnet.

Sichter
(Graf Isolan), Hindemith

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