Research Problems in Semantic
Web Search
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Varish Mulwad
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Agenda
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• Introduction
• Swoogle
• Swoogle’s 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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Your Agent
Web
Possible because:
Data is in machine understandable
form like – RDF, OWL
Dr.Finin’s
FOAF Profile
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
• Keyword based search
• Searches Ontologies and
Instance Data
Sindice
• Indexes on URI, IFP,
keywords
• Use of Hadoop Architecture
SWSE
• Pipelined Architecture for
Crawling
Watson
• Implicit relations between
SWDs
Falcon
• Class Subsumption
Reasoning
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Issues
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Crawling
• Swoogle’s 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 d’Aquin 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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