Query Relaxation Using Malleable Schemas

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Query Relaxation Using Malleable Schemas

• Xuan Zhou, Julien Gaugaz, Wolf-Tilo Balke,
  Wolfgang Nejdl
• L3S Research Center
• Leibniz University
• Hanover, Germany

Presented by Aaron Stewart BYU CS 652 Spring 2009
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Problem

?
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Problem

• Multiple data sources
• Unmatched schemas

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Approach

1. Malleable schemas
2. Discover correlations
3. Relax user queries

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Malleable Schemas

• Allow duplicate fields
• Allow related fields

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Malleable Schemas
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Malleable Schemas
first_name, sur_name
name
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Malleable Schemas
body
contents
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In Practice Tables

• a malleable schema contains imprecise and
  overlapping definitions of attributes or
  relationships.
• In this way, a malleable schema can capture such
  heterogeneous data structures as in Figure 1.

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In Practice Tables
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In Practice Tables
Attributes (database fields, columns)
Entities (database records, rows)
Equivalently Distinct tables
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Query Relaxation Planning

• Multiple queries
• Different columns or tables
• As few queries as possible
• Exponential number of relaxed queries
• Evaluate in order of precision
• Stop at k results

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Query Relaxation Planning
relaxed attribute
child attributes
A1
A2
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Query Relaxation Planning

• A relaxed query always yields better precision
  than its child queries, so that it should always
  be evaluated prior to its child queries

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Parent/Child Relationship

• We would think A is the parent, and A1 and A2 are
  the children, but
• Put them in order of correlation probability
• If P(AA1) gt P(AA2)
• Then A gt A1 gt A2

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Query Relaxation Planning
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Query Relaxation
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Experiments

• Data sets
• IMDB Movies
• Amazon.com DVDs and VHS videos

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Results
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Results
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Results
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Analysis

• Strengths
• Handles mixed schemas
• Well-designed algorithms (IMO)
• Future work
• Speed