1. ConQuer: Efficient Management of Inconsistent Databases Presented by: Presented by: Ariel Fuxman (Univ. of Toronto) Ariel Fuxman (Univ. of Toronto) Joint work with: Renée J. Miller (Univ of Toronto) Diego Fuxman (Univ. Nacional del Sur)

2. Ariel Fuxman, Diego Fuxman, Renée J. Miller 2 A system designed to answer SQL queries over inconsistent databases A system designed to answer SQL queries over inconsistent databases ConQuer 130KMary 110KMary 400KPaul 200KPeter 40KPeter IncomeName name should be the key INCONSISTENT DATABASE

3. Ariel Fuxman, Diego Fuxman, Renée J. Miller 3 One Application Sales Shipping Customer Support Web Forms Demographic Data IntegratedCustomerDatabase Customer Relationship Management (CRM)

4. Ariel Fuxman, Diego Fuxman, Renée J. Miller 4 Disagreement Between Sources Which tuple for Peter should we delete? Which tuple for Peter should we delete? Removing both tuples loses consistent information Removing both tuples loses consistent information Deciding the correct income may require human intervention Deciding the correct income may require human intervention 110K… 20 Union Street Mary 400K… 100 Bloor Street Paul …. … 276 College Street address 40KPeter incomename 400K… 100 Bloor Street Paul 130K… 20 Union Street Mary …. … 276 College Street address 200KPeter incomename sales web

5. Ariel Fuxman, Diego Fuxman, Renée J. Miller 5 Inconsistent Integrated Database name…income Peter…40K Paul…400K Mary…110K name…incomePeter…200K Paul…400K Mary…130K name…incomePeter…40K Peter…200K Paul…400K Mary…110K Mary…130K Sales Web Integrated Database Transfer all conflicting tuples to the integrated database INCONSISTENT DATABASE

6. Ariel Fuxman, Diego Fuxman, Renée J. Miller 6 Query Answering q=“Get customers who make more than 100K” 130K 110K 400K 200K 40K income web sales sales/web web sales Mary Mary Paul Peter Peter name Peter,Paul,Mary Peter should NOT be offered a Platinum card!! Offering a Platinum credit card…

7. Ariel Fuxman, Diego Fuxman, Renée J. Miller 7 Semantics of Query Answering Get customers who possibly make more than 100K Get customers who possibly make more than 100K Peter, Paul, Mary Peter, Paul, Mary Get customers who certainly make more than 100K Get customers who certainly make more than 100K Paul, Mary Paul, Mary CONSISTENTANSWER [Arenas et al. 99] custidincome Peter40Ksales Peter200Kweb Paul400Ksales/web Mary110Ksales Mary130Kweb

8. Ariel Fuxman, Diego Fuxman, Renée J. Miller 8RepairsPeter40K Paul400K Mary110K Peter40KPaul400K Mary130K Peter200KPaul400K Mary110K Peter200KPaul400K Mary130K 130K 110K 400K 200K 40K income web sales sales/web web sales Mary Mary Paul Peter Peter custid Inconsistent database Repairs Key: custid

9. Ariel Fuxman, Diego Fuxman, Renée J. Miller 9 CONSISTENT ANSWERS Answers obtained no matter which repair we choose Consistent Query Answers Peter40K Paul400K Mary110K Peter40KPaul400K Mary130K Peter200KPaul400K Mary110K Peter200KPaul400K Mary130K q=“Get customers who make more than 100K” q q q q CONSISTENTANSWER={Paul,Mary} Repairs Mary Paul Peter Mary Paul Mary Paul Mary Paul Peter

10. Ariel Fuxman, Diego Fuxman, Renée J. Miller 10 Problem Potentially HUGE number of repairs!

11. Ariel Fuxman, Diego Fuxman, Renée J. Miller 11 ConQuer ConQuer is a system designed to compute consistent answers efficiently ConQuer is a system designed to compute consistent answers efficiently avoids explicit construction of repairs avoids explicit construction of repairs reuses commercial database technology reuses commercial database technology

12. Ariel Fuxman, Diego Fuxman, Renée J. Miller 12 Commercial database engine ConQuer’s Solution Query q Keys Keys Rewritten Q * ConQuer’sRewritingAlgorithm [ICDT 05] [SIGMOD 05] Inconsistentdatabase Consistent answer to q

13. Ariel Fuxman, Diego Fuxman, Renée J. Miller 13 Contributions Rewriting algorithm Rewriting algorithm From a large class of SPJ SQL queries From a large class of SPJ SQL queries Into SQL queries Into SQL queries Rewriting for queries with grouping and aggregation Rewriting for queries with grouping and aggregation Optimized rewriting Optimized rewriting Exploits precomputed information, if available Exploits precomputed information, if available Experimental evaluation Experimental evaluation Large databases Large databases TPC-H queries TPC-H queries

14. Ariel Fuxman, Diego Fuxman, Renée J. Miller 14 Demo Present a case study of an inconsistent database about airports and cities Present a case study of an inconsistent database about airports and cities Explain the automatically generated rewritings Explain the automatically generated rewritings Deal with Select-Project-Join queries with grouping and aggregation Deal with Select-Project-Join queries with grouping and aggregation

15. Ariel Fuxman, Diego Fuxman, Renée J. Miller 15 ConQuer papers A. Fuxman, E. Fazli, and R. J. Miller. ConQuer: Efficient Management of Inconsistent Databases, SIGMOD 2005. 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. A. Fuxman and R. J. Miller. First-Order Query Rewriting for Inconsistent Databases, ICDT 2005.