文章基本信息

标题：Enumerating Homomorphisms
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作者：Andrei A. Bulatov ; Victor Dalmau ; Martin Grohe 等
期刊名称：LIPIcs : Leibniz International Proceedings in Informatics
电子版ISSN：1868-8969
出版年度：2009
卷号：3
页码：231-242
DOI：10.4230/LIPIcs.STACS.2009.1838
出版社：Schloss Dagstuhl -- Leibniz-Zentrum fuer Informatik
摘要：The homomorphism problem for relational structures is an abstract way of formulating constraint satisfaction problems (CSP) and various problems in database theory. The decision version of the homomorphism problem received a lot of attention in literature; in particular, the way the graph-theoretical structure of the variables and constraints influences the complexity of the problem is intensively studied. Here we study the problem of enumerating all the solutions with polynomial delay from a similar point of view. It turns out that the enumeration problem behaves very differently from the decision version. We give evidence that it is unlikely that a characterization result similar to the decision version can be obtained. Nevertheless, we show nontrivial cases where enumeration can be done with polynomial delay.