Title :
First-order definable retraction problems for posets and reflexive graphs
Author :
Dalmau, Víctor ; Krokhin, Andrei ; Larose, Benoit
Author_Institution :
Dept. of Technol., Pompeu Fabra Univ., Barcelona, Spain
Abstract :
A retraction from a structure P to its substructure Q is a homomorphism from P onto Q that is the identity on Q. We present an algebraic condition which completely characterises all posets and all reflexive graphs Q with the following property: the class of all posets or reflexive graphs, respectively, that admit a retraction onto Q is first-order definable.
Keywords :
combinatorial mathematics; formal logic; graphs; algebraic condition; definable retraction problems; first-order retraction problems; homomorphism; posets; reflexive graphs; structure P; substructure Q; Artificial intelligence; Chromium; Computational complexity; Computer science; Logic; Vocabulary;
Conference_Titel :
Logic in Computer Science, 2004. Proceedings of the 19th Annual IEEE Symposium on
Print_ISBN :
0-7695-2192-4
DOI :
10.1109/LICS.2004.1319617
