160 search results - page 1 / 32 » Homomorphism preservation theorems |
JACM
2008
14 years 10 months ago
2008
PODS
2004
ACM
15 years 10 months ago
2004
ACM
Unions of conjunctive queries, also known as select-project-join-union queries, are the most frequently asked queries in relational database systems. These queries are definable b...
GC
2010
Springer
14 years 8 months ago
2010
Springer
A directed graph has a natural Z-module homomorphism from the underlying graph’s cycle space to Z where the image of an oriented cycle is the number of forward edges minus the n...
JSYML
2010
14 years 4 months ago
2010
A set A of vertices of a graph G is called d-scattered in G if no two d-neighborhoods of (distinct) vertices of A intersect. In other words, A is d-scattered if no two distinct ver...
JCT
2007
14 years 9 months ago
2007
We conjecture that every planar graph of odd-girth 2k + 1 admits a homomorphism to Cayley graph C(Z2k+1 2 , S2k+1), with S2k+1 being the set of (2k + 1)vectors with exactly two co...