COOPERATION STRATEGIES FOR INFORMATION INTEGRATION

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COOPERATION STRATEGIES FORINFORMATION INTEGRATION
Istituto di Informatica - Università degli studi
di Ancona

• Maurizio Panti, Luca Spalazzi, Loris Penserini
• panti,spalazzi,pense_at_inform.unian.it

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Talk Overview

• Motivations and Goals
• Local strategies
• Cooperation strategies
• the choice of partners
• the choice of queries
• the choice of answers
• Discussion

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Motivation

• Information systems are collections of
  information sources and information consumers
• Distributed
• Heterogeneous
• at physical level
• at logical level
• at conceptual level (names and schemas)
• Dynamic
• changes of information sources or their schemas
• changes of information consumers or their needs

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Goal

• Rewriting a consumers query into queries to
  specific information sources
• when we have
• a distributed, heterogeneous, and strongly
  dynamic information system.

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Related Work

• Usually query rewriting and information
  integration systems adopt the
• Mediator Architecture
• TSIMMIS, Squirrel, WHIPS, Carnot, SIMS,
  Information Manifold, Infomaster
• dynamic sources systems are overloaded with
  expensive updating operations
• dynamic consumers systems do not perform user
  profiling.

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Information Source

• wrapper
• a description logic as data modelling and query
  language e.g. C-Classic
• source query processing is based on rewriting
  query using views over the local source
  adapted by Beeri, Levy, Rousset

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Mediator

• mediated schema
• a description logic as data modelling and query
  language e.g. C-Classic
• query processing is based on rewriting query
  using views over the distributed sources
  adapted by Beeri, Levy, Rousset

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Rewriting query using views
Rewriting Composition of rewriting of retrieved
concepts
Retrieval Conjunction of concepts that are
maximally contained in the query
query Q "pub.(ai ? db) ? "pub.acm
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Query Execution
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Local Failures

• In query rewritingthe mediator is not able to
  rewrite (some or all the components) of the input
  query.
• In query executionthe mediator is not able to
  execute (some or all the components) of the
  rewrited query.

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Cooperation Strategies

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Cooperation with MediatorsAsking for Rewriting
Mediator M
Mediator N
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Cooperation with MediatorsAsking for Data
Mediator M
Mediator N
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Cooperation with Sources
Mediator M
Mediator N
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Strategy Comparison
m number of mediators s number of sources s
number of sources that cooperate with Ni
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Strategy Comparison
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Conclusion

• 1st scenario (s ms)
• mediators can be used for user profiling,
• mediators can be used to solve name heterogeneity
  and integrate data,
• in order to solve schema heterogeneity, for a
  mediator the most efficient and effective
  strategy is to directly cooperate with sources,
• in order to update its schemas, for a mediator a
  lazy approach can be not appropriate.

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Conclusion

• 2nd scenario (s gtgt ms)
• mediators can be used for user profiling,
• the most efficient strategy is the cooperation
  with other mediators,
• cooperation with wrappers is useful only when
  mediators are not able to rewrite a given query,
• in order to update its schemas, for a mediator a
  lazy approach is appropriate.

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Ms Mediated Schema
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Rewriting query using views
Composition of rewriting of retrieved concepts
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Rewriting query using views
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Local Failure in Query Rewriting
query Q"pub.(ai?db)?"affiliation.Stanford
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Local Failure in Query Execution
no answer
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Cooperation with MediatorsAsking for Rewriting
retrieved concepts"pub.acm_tocl, "pub.acm_tods
rewriteview("pub.acm_tocl),view("pub.acm_tods)
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Cooperation with MediatorsAsking for Rewriting
Mediator M
rewriteview("pub.acm_tocl),view("pub.acm_tods)
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Cooperation with MediatorsAsking for Data
retrieved concepts"pub.acm_tocl, "pub.acm_tods
rewriteview("pub.acm_tocl),view("pub.acm_tods)
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Cooperation with MediatorsAsking for Data
rewriteview("pub.acm_tocl),view("pub.acm_tods)
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Cooperation with MediatorsAsking for Data
rewriteview("pub.acm_tocl),view("pub.acm_tods)
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Cooperation with Sources
retrieved"pub.acm_ccs,"pub.acm_jacm,"pub.acm_tod
s
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Redundancy
Cn(M) mediated schema of M after n interactions
with N C(N) mediated schema of N
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Recall
Cn(M) mediated schema of M after n interactions
with S1, Sn n information need of a consumer(a
view of S1, Sn )
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Precision
Cn(M) mediated schema of M after n interactions
with S1, Sn n information need of a consumer(a
view of S1, Sn )
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Ns Mediated Schema
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Ms Mediated Schema (updated)
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Ms Mediated Schema (updated)
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Ms Mediated Schema (updated)
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Cooperation with Mediators
Theorem. Cn(M) mediated schema of M after n
interactions with N C(N) mediated schema of N
redundancy
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Cooperation with Mediators
Theorem. Cn(M) mediated schema of M after n
interactions with N n information need of a
consumer(a view of S1, Sn )
recall
precision
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Cooperation with Sources
Theorem. Cn(M) mediated schema of M after n
interactions with S1, Sn n information need of
a consumer(a view of S1, Sn )
recall
precision