Transcript slides
Towards a Proxy Architecture for
Semantic Web Services
Eric Rozell, Tetherless World Constellation (http://bit.ly/erozell)
Workshop Scenario
• Scenario 1: Company A is hosting
services on multiple Cloud instances on
different continents, and needs to adapt
its resource consumption through the
different cloud management interfaces.
It needs to create an uniform view of
those computing resources
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Heterogeniety in Web
Service Semantics
• Different cloud management systems likely
provide heterogeneous syntax and semantics
for their Web Service offerings
• Syntactic Descriptions (w/ Annotations)
– SAWSDL, OpenSearch, OData, …
• Ontologies
– OWL-S, SWSO, WSMO, …
• This is a good thing!
– Choice of Syntax and Semantics α
Potential Use Cases
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Motivation for Proxy
Architecture
• Clients designed for specific syntactic
descriptions and ontologies
• What if new syntactic description uses
“understood” ontology?
• Why require clients to understand
syntactic descriptions?
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S2S Framework
• Part of NSF funded Semantic eScience Framework
Project (SeSF Project)
• Originally designed for oceanographic
“data dashboard”
• Used heterogeneous data and services
– IOBIS: service for biogeographic data [DiGIR]
– HydroBase: database of hydrographic profiles [cmd line]
– BCO-DMO: data and metadata services for biological and
chemical oceanography [SQL]
– Interridge: hydrothermal vents database [Excel]
• Designed an ontology around common “operations”
used across each data source/service
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S2S “Application
Integration” Ontology
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S2S Instances Example
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S2S Syntactic
Description Example
• In OpenSearch…
<Url type=“application/json”
rel=“s2s-core:DatasetTableQuery”
template=“http://aquarius.tw.rpi.edu/s2s/BCODMO/search.php?request=dataTable&bbox={ge
o:box?}&startDate={time:start?}&endDate=
{time:end?} …” />
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S2S Syntactic
Description Example
• In SAWSDL…
<wsdl:description … >
<wsdl:types>
<xs:element name=“input>
<xs:element name=“bbox” … sawsdl:modelReference=“geo:box” />
<xs:element name=“startTime” … sawsdl:modelReference=“time:start” />
…
</xs:element>
<xs:element name=“output” … sawsdl:modelReference=“s2s-core:HtmlTable” />
</wsdl:types>
<wsdl:interface>
<wsdl:operation … sawsdl:modelReference=“s2s-core:DatasetTableQuery”>
<wsdl:input element=“input”/>
<wsdl:output element=“output” />
</wsdl:operation>
</wsdl:interface>
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</wsdl:description>
S2S Widget Example
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S2S Architecture
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S2S Framework
• Goal: Keep client-server interaction as
simple as possible
• Used OpenSearch for description of
Web services (w/ semantic annotations)
• Designed precursor to proxy
architecture
• Facilitated reuse of UI “widgets” for
search and visualization
• Limited to stateless search and retrieval
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Towards a More General
Proxy Architecture
• Given that the S2S paradigm is limited
to stateless search and retrieval…
• Is this “proxy architecture” applicable
more generally to Semantic Web
Services?
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Example Semantic Web
Service Interaction
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Example Semantic Web
Service Interaction
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Example Semantic Web
Service Interaction
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Example Semantic Web
Service Interaction
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Example Semantic Web
Service Interaction
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Example Semantic Web
Service Interaction
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Example Semantic Web
Service Interaction
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Example Semantic Web
Service Interaction
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Alternative Semantic
Web Service Interaction
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Alternative Semantic
Web Service Interaction
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Alternative Semantic
Web Service Interaction
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Alternative Semantic
Web Service Interaction
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Alternative Semantic
Web Service Interaction
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Alternative Semantic
Web Service Interaction
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Benefits
• Reduces complexity of clients
– Not required to “understand” syntactic
descriptions of Web Services
– Fewer requests made by clients
• Extensibility
– Adaptable to multiple syntactic descriptions
(provided compatibility with SWS ontology)
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Things to Consider for
W3C
• Recommending communication protocol
for Semantic Web Service proxies
– RDF or JSON
• Vocabulary considerations (would a generic
architecture would adapt to new ontologies?)
– Defining HTTP methods
• Soliciting implementations for the proxy
architecture
– Semantic Automated Discovery and
Integration (SADI)
– OWL-S API
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Conclusion
• S2S proxy architecture has shifted
much of the burden for Web Service
interaction away from the client
• A more general proxy architecture may
be useful to increase adoption and use
of Semantic Web Services
• There is a need for W3C
recommendations for this to move
forward
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Questions?
• Thanks for listening!
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S2S Resources
• Faceted browser for Biological and Chemical
Oceanography Data Management Office
(BCO-DMO) [http://bit.ly/bcodmo-demo]
• Faceted browser for International Open
Government Data Search (IOGDS)
[http://bit.ly/twiogdc]
• S2S Project Page [http://bit.ly/twcs2s]
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