ConQuer: Efficient Management of Inconsistent Databases

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ConQuer Efficient Management of Inconsistent
Databases

• Presented by
• Ariel Fuxman (Univ. of Toronto)
• Joint work with
• Renée J. Miller (Univ of Toronto)
• Diego Fuxman (Univ. Nacional del Sur)

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ConQuer

• A system designed to answer SQL queries over
  inconsistent databases

Income
Name
40K
Peter
200K
Peter
INCONSISTENT DATABASE
400K
Paul
110K
Mary
130K
Mary
name should be the key
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One Application

• Customer Relationship Management (CRM)

Sales
Integrated Customer Database
Shipping
Customer Support
Web Forms
Demographic Data
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Disagreement Between Sources

• Which tuple for Peter should we delete?
• Removing both tuples loses consistent
  information
• Deciding the correct income may require human
  intervention

address
income
name
.
276 College Street
40K
Peter
sales
400K

100 Bloor Street
Paul
110K

20 Union Street
Mary

address
income
name
.
276 College Street
200K
Peter
web
400K

100 Bloor Street
Paul
130K

20 Union Street
Mary
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Inconsistent Integrated Database
Transfer all conflicting tuples to the integrated
database
Integrated Database
Sales
INCONSISTENT DATABASE
Web
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Query Answering
Offering a Platinum credit card

• qGet customers who make more than 100K

Peter,Paul,Mary
Peter should NOT be offered a Platinum card!!
income
name
40K
sales
Peter
200K
web
Peter
400K
sales/web
Paul
110K
sales
Mary
130K
web
Mary
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Semantics of Query Answering

• Get customers who possibly make more than 100K
• Peter, Paul, Mary
• Get customers who certainly make more than 100K
• Paul, Mary

CONSISTENT ANSWER Arenas et al. 99
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Repairs
Repairs
Inconsistent database
income
custid
40K
sales
Peter
200K
web
Peter
400K
sales/web
Paul
110K
sales
Mary
130K
web
Mary
Key custid
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Consistent Query Answers
qGet customers who make more than 100K
Repairs
q
Paul
Mary
CONSISTENT ANSWER Paul,Mary
CONSISTENT ANSWERSAnswers obtained no matter
which repair we choose
q
Paul
Mary
Peter
q
Paul
Mary
Peter
q
Paul
Mary
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Problem

• Potentially HUGE number of repairs!

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ConQuer

• ConQuer is a system designed to compute
  consistent answers efficiently
• avoids explicit construction of repairs
• reuses commercial database technology

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ConQuers Solution
Query q Keys
Consistent answer to q
ConQuers Rewriting Algorithm ICDT 05 SIGMOD
05
Commercial database engine
Inconsistent database
Rewritten Q
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Contributions

• Rewriting algorithm
• From a large class of SPJ SQL queries
• Into SQL queries
• Rewriting for queries with grouping and
  aggregation
• Optimized rewriting
• Exploits precomputed information, if available
• Experimental evaluation
• Large databases
• TPC-H queries

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Demo

• Present a case study of an inconsistent database
  about airports and cities
• Explain the automatically generated rewritings
• Deal with Select-Project-Join queries with
  grouping and aggregation

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ConQuer papers

• A. Fuxman, E. Fazli, and R. J. Miller. ConQuer
  Efficient Management of Inconsistent Databases,
  SIGMOD 2005.
• A. Fuxman and R. J. Miller. First-Order Query
  Rewriting for Inconsistent Databases, ICDT 2005.