Set constraints and topology

✍ Scribed by Franck Seynhaeve

• Book ID: 104136569
• Publisher: Elsevier Science
• Year: 2001
• Tongue: English
• Weight: 82 KB
• Volume: 80
• Category: Article
• ISSN: 0020-0190
• DOI: 10.1016/s0020-0190(01)00157-0

✦ Synopsis

Set constraints are inclusions between expressions denoting sets of trees. Such expressions are first-order terms with or without set operators. Many results in the literature on set constraints are topological in flavor. In this paper, we notice that the set of solutions of a system of set constraints of the class (PNSC) (class of positive and negative set constraints) is the intersection of a closed set and of an open set. This allows us to prove that the class (PSCP) (class of positive set constraints with projection) is strictly more expressive than the class (PNSC).