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Summary: Hypertree-width and related invariants
Isolde Adler
Szeged, 23rd September 2006
Outline
1. Hypertree-width: Motivation and Definition
2. The Robber and Marshals Game
3. Non-monotone marshals are stronger
4. 3 + monotone marshals can replace 1 non-monotone marshal
5. Conclusion
ISOLDE ADLER HYPERTREE-WIDTH AND RELATED INVARIANTS 2/38
Motivation: The homomorphism problem
HOM
Input: relational structures A, B.
Question: h : A
hom
- B?
· equivalent to CSP, to CQ evaluation on relational databases
· NP-complete
Goal: Find tractable restrictions of HOM
ISOLDE ADLER HYPERTREE-WIDTH AND RELATED INVARIANTS 3/38
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