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Durham University

Computer Science


Publication details for Professor Iain Stewart

Madelaine, F.R. & Stewart, I.A. (2003). Some problems not definable using structure homomorphisms. Ars Combinatoria 67: 153-159.

Author(s) from Durham


We exhibit some problems definable in Feder and Vardi's logic MMSNP that are not in the class CSP of constraint satisfaction problems. Whilst some of these problems have previously been shown to be in MMSNP (that is, definable in MMSNP) but not in CSP, existing proofs are probabilistic in nature. We provide explicit combinatorial constructions to prove that these problems are not in CSP and we use these constructions to exhibit yet more problems in MMSNP that are not in CSP.