The Complexity of Positive First-Order Logic without Equality
The Complexity of Positive First-Order Logic without Equality
We study the complexity of evaluating positive equality-free sentences of first-order (FO) logic over a fixed, finite structure B . This may be seen as a natural generalisation of the nonuniform quantified constraint satisfaction problem QCSP( B ). We introduce surjective hyper-endomorphisms and use them in proving a Galois connection …