Homomorphism Problems for First-Order Definable Structures
نویسندگان
چکیده
We investigate several variants of the homomorphism problem: given two relational structures, is there a homomorphism from one to the other? The input structures are possibly infinite, but definable by first-order interpretations in a fixed structure. Their signatures can be either finite or infinite but definable. The homomorphisms can be either arbitrary, or definable with parameters, or definable without parameters. For each of these variants, we determine its decidability status. 1998 ACM Subject Classification F.4.1 [Mathematical Logic] Model theory, F.4.3 [Formal Languages] Decision problems
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