Publication details for Professor Iain StewartMadelaine, F.R. & Stewart, I.A. (2003). Some problems not definable using structure homomorphisms. Ars Combinatoria 67: 153-159.
- Publication type: Journal Article
- ISSN/ISBN: 0381-7032
- Keywords: Constraint satisfaction. CSP. MMSNP.
- Further publication details on publisher web site
- Durham Research Online (DRO) - may include full text
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.