The document discusses techniques for applying data distribution information to algebraic queries on a global conceptual schema. It outlines methods for optimizing queries through data localization and advanced reduction techniques that target both horizontal and vertical fragmentation. The ultimate goal is to achieve query simplification and enhance performance by minimizing unnecessary computations.

1.  – Input:
 Algebraic query on global conceptual schema
 – Purpose:
 ∗Apply data distribution information to the
algebra operations and determine which
fragments are involved
 ∗Substitute global query with queries on
fragments
 ∗Optimize the global query
Data Localization

3. Provides Parallelism

4. Eliminates Unnecessary Work

5. Data Localizations Issues
 •Various more advanced reduction techniques are possible to generate
simpler and optimized queries.
 •Reduction of horizontal fragmentation (HF)
 –Reduction with selection
 –Reduction with join
 •Reduction of vertical fragmentation (VF)

 –Find empty relations

6. Reduction of horizontal fragmentation (HF) with
Selection

8. Reduction of horizontal fragmentation
(HF) with Join

10. Data Localizations Issues – Reduction
for VF ..