RDF from the Java Perspective

1
RDF from the Java Perspective
2
Three-Step Recipe

• Create RDF metadata in Java.
• Serialize my RDF to RDF/XML.
• Interface with the information service?
• Library support
• Jena (com.hp.hpl.jena.rdf.model)
• HttpClient (org.apache.commons.httpclient)

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Data Stream Management

• Collection of metadata
• Statistics
• Content-Provider
• Optimization
• Use of information service
• Metadata storage
• Query interface

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Data Sources in Data Stream Management
Content-Providers

• Publish multiple data streams
• Content-Provider metadata
• ID
• Stream metadata
• ID
• Structural information (DTD)
• Frequency

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Queries on Metadata

• Which streams are in general available at content
  providers?
• Which streams are availabe at content provider
  notekemper15.informatik.tu-muenchen.de?
• Which content providers serve the stream with
  identifier stream-1?
• What is the DTD of stream-1 at notekemper15?

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The RDF Model
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Creating the RDF Model in Java

• Create Model-Instance
• Resources
• notekemper15 (ContentProvider)
• stream-1 (Stream)
• Properties
• dtd, frequency (of streams)
• Creating Triples (Subject, Predicate, Object)
• (notekemper15, stream, stream-1)
• (stream-1, dtd, lt!ELEMENT strom (element)gt)

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Creating the RDF-XML

• RDFWriter serializes RDF-Model

ltrdfRDF xmlnsj.0"http//www.gac-grid.org/na
mespaces/streaming/" xmlnsrdf"http//www.w3.
org/1999/02/22-rdf-syntax-ns" gt
ltrdfDescription rdfabout"http//notekemper15.in
formatik.tu-muenchen.de8080/wsrf/services/streamg
lobe/ContentProviderFactory"gt
ltj.0idgtTUMlt/j.0idgt ltj.0stream
rdfresource"stream-2"/gt
ltj.0stream rdfresource"stream-1"/gt
lt/rdfDescriptiongt ltrdfDescription
rdfabout"stream-2"gt
ltj.0idgtstream-2lt/j.0idgt
ltj.0dtdgtlt!ELEMENT stream (row)gtlt/j.0dtdgt
ltj.0frequencygt3lt/j.0frequencygt
lt/rdfDescriptiongt ltrdfDescription
rdfabout"stream-1"gt
ltj.0idgtstream-1lt/j.0idgt
ltj.0dtdgtlt!ELEMENT strom (row)gtlt/j.0dtdgt
ltj.0frequencygt11lt/j.0frequencygt
lt/rdfDescriptiongt lt/rdfRDFgt
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Connecting the Information Service

• Create new HttpClient
• Create PutMethod to access Information
  Servicehttp//mintaka.aip.de24000/context/stream
  ing
• Set content of PutMethod to generated RDF/XML
• Execute the PutMethod with the HttpClient

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Submit Query to Information Service

• Return all Content-Providers and their available
  streams including stream-ids and Document Type
  Definitions
• PREFIX streamlthttp//www.gac-grid.org/namespa
  ces/streaming/gt PREFIX rdflthttp//www.w3.org/1999
  /02/22-rdf-syntax-nsgtSELECT ?cp ?stream ?id
  ?dtd WHERE ?cp streamstream ?stream .
  ?stream streamid ?id .
  ?stream streamdtd ?dtd .

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RDF Workshop

• Thank You for Your Attention!
• Further Questions?