Research Problems in Semantic Web Search

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Research Problems in Semantic Web Search
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• Varish Mulwad

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Agenda
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• Introduction
• Swoogle
• Swoogles Competition
• Sindice
• Semantic Web Search Engine (SWSE)
• Watson
• Falcon
• Research Problems and Issues with Swoogle
• References

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Introduction
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Web
Your Agent
Dr.Finins FOAF Profile
Possible because Data is in machine
understandable form like RDF, OWL But how will
agent find all this data ? Search Engines ?
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Introduction
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Traditional Search Engine Results
Semantic Web Search Engine Results
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Swoogle
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• Swoogle is a crawler based indexing and retrieval
  system for Semantic Web
• Swoogle crawls and discovers documents written in
  RDF,OWL
• Swoogle classifies a Semantic Web Document(SWD)
  as
• Semantic Web Ontology (SWO) Defines new terms
• Semantic Web Databases (SWDB) Makes assertions
  about individuals

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Swoogle
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• SWOOGLE DEMO

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Swoogle Architecture
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Swoogle Architecture
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• SWD Discovery Component
• Google crawler using the Google web service
• Filetypes with extensions .rdf, .owl, .n3
• Google limits only 1000 results per query
• A focussed crawler
• Crawls documents within a given website
• Extension and Focus constraints
• A Swoogle crawler
• Jena based crawler
• Explores Semantic Links between SWDs

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Swoogle Architecture
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• Metadata Creation
• Basic Metadata
• Encoding RDF/XML, N-Triple, N3
• Language RDF, RDFS, OWL, DAML OIL
• OWL Species OWL-LITE, OWL-DL, OWL-FULL
• Relations among SWDs
• Reference relationship among SWDs
• Inter ontology relationships

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Swoogle Architecture
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• Data analysis component
• Classification of SWD as SWO or SWDB
• Compute rank of SWD
• Web based interface
• Human User Interface http//swoogle.umbc.edu
• Web Services using REST interface
• Agent Service

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Sindice
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• Created at Digital Enterprise Research Institute
  (DERI)
• Key features of Sindice include
• Sindice collects SWDs and indexes them on
  resource URIs, Inverse Functional
  Properties(IFPs) and keywords
• Sindice uses the Hadoop parallel architecture

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Sindice
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• Inverse Functional Property (IFP) An OWL
  cardinality restriction
• Sincdice uses three indexes
• URI index
• IFP index
• Keyword index
• Benefits - Faster retrieval of data

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Sindice
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• Hadoop architecture is used in the following
  manner
• Sindice employs Hadoop/Nutch to distribute
  crawling job across multiple machines
• Collected data is stored in the Hbase distributed
  column based store
• Efficient handling of large datasets across the
  cluster using a MapReduce implementation

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Sindice
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• SINDICE DEMO

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SWSE
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• Semantic Web Search Engine (SWSE) is also a
  Semantic Web Search Engine created at Digital
  Enterprise Research Institute (DERI)
• SWSE uses a Multicrawler a pipelined
  architecture for crawling

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Watson
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• Created at Knowledge Management Institute at the
  UK Open University
• Major Design Principles
• Considers explicit and implicit relations between
  Ontologies
• Ranking of Ontologies with focus on quality over
  popularity

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Watson
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• WATSON DEMO

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Falcon
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• Falcon is a Semantic Web Search engine created at
  the Institute of Web Science in China
• Falcon allows keyword based queries on
• Objects
• Concepts
• Documents
• Falcon performs class subsumption reasoning

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Falcon
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• FALCON DEMO

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Summary
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• Swoogle

• Others

• Sindice
• Indexes on URI, IFP, keywords
• Use of Hadoop Architecture
• SWSE
• Pipelined Architecture for Crawling
• Watson
• Implicit relations between SWDs
• Falcon
• Class Subsumption Reasoning

• Keyword based search
• Searches Ontologies and Instance Data

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Issues
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• Crawling
• Swoogles crawler is running as a single thread
  on one machine
• Limits the number of SWDs dicovered and revisted
• Possible Solutions
• Use of Hadoop Architecture
• Use of Grub

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Other Issues
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• Crawling large structured Datasets like DBPedia
• More reasoning
• More services

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References
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• Li Ding et al., "Swoogle A Search and Metadata
  Engine for the Semantic Web", Proceedings of the
  Thirteenth ACM Conference on Information and
  Knowledge Management, November 2004.
• P. Mika, G. Tummarello Web Semantics in the
  Clouds, IEEE Intelligent Systems, Volume 23 ,
  Issue 5 (September 2008)
• E. Oren, R.Delbru, M. Catasta, R. Cyganiak, H.
  Stenzhorn, G.
• Tummarello Sindice.com A document-oriented
  lookup index for open linked data. In
  International Journal of Metadata, Semantics and
  Ontologies, 3(1), 2008.
• Mathieu dAquin et al., Watson A Gateway for
  the Semantic Web ,Poster session of the European
  Semantic Web Conference, ESWC 2007
• Gong Cheng, Weiyi Ge, Honghan Wu, Yuzhong Qu ,
  Searching Semantic Web Objects Based on Class
  Hierarchies In WWW 2008 Workshop on Linked Data
  on the Web, 2008

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Questions?
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