A Survey on Disk Oriented Querying and Reasoning on the Semantic Web

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A Survey on Disk Oriented Querying and Reasoning
on the Semantic Web
Computer Languages and Computing Science
Department University of Malaga Spain

• María del Mar Roldán , José F. Aldana

http//khaos.uma.es
Spanish junior researchers fight for employment
rights
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We need (efficient and scalable) TOOLS for
storing and querying OWL ontologies
Integration not trivial
Study how different logical and physical
(persistent) storage models influence on the
querying and reasoning mechanisms performance
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Objectives

• Describing seven systems (SESAME, JENA, KAON,
  KOWARI, DLDB, DLP-IM, IS) which uses database
  technology to both represent knowledge
  persistently and query this knowledge in the
  Semantic Web context.
• According to four features
• Ontology definition language
• Storage model
• Query language
• Reasoning mechanisms
• Obtaining conclusions and needs

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Evaluation Framework (I)
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Evaluation Framework (II)
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Ontology Definition Language

• From RDF to OWL

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Storage Model

• Databases without specific physical
  representation and access paths.

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Query language

• Usually translated to SQL or Datalog
• No distribution

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Reasoning Mechanisms (Tbox)

• Concept subsumption
• No implementation homogeneity

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Reasoning Mechanisms (Abox)

• Instances Retrieval
• No implementation homogeneity

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Current tools (Using database technology)
Our Proposal
Databases as instances warehouses
Select the best logical model
Simple logical models
No physical representation of the knowledge
Select the best physical storage structures and
indexes
Few reasoning mechanisms (subsumption) and simple
query languages
Implement complex reasoning mechanisms and query
language
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Current tools (Using database technology)
Methodology
In general (for all OWL ontologies)
For some specific applications (biology)
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How to proceed (Future tends)

• Defining complex reasoning mechanisms
• Defining our query language complex concepts
  conjunctive queries
• Implementing the reasoning mechanisms and the
  query language using several persistent storage
  models (relational databases, logical databases,
  XML databases)

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How to proceed (Future tends)

• Designing different physical storage for the
  previous models
• Getting performance measures and doing analysis
• Obtaining conclusions and using them to define a
  set of recommendations/methodology

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Problems.

• Technical Problems
• Complexity of the language (DL formalism)
• No good OWL parser
• BIG QUESTIONS TO DEAL WITH
• Face OWA-CWA impedance mismatch in the query
  language
• Analyze (New) Trade-offs between expressiveness
  and efficiency (when reasoning in secondary
  memory)

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A Survey on Disk Oriented Querying and Reasoning
on the Semantic Web
Computer Languages and Computing Science
Department University of Malaga Spain

• María del Mar Roldán , José F. Aldana

http//khaos.uma.es
Spanish junior researchers fight for employment
rights