3Zś>:Rdn&ru;HV_6AqֵQuRoHJQlf4S"pʨ$"v$[ɂw 1EB[҄\um3P5u_ y@)N+fjsF6zZi|3Q'jDy7J֛S`3mNV[{ '2S3#zOO)CG5 "&"1 7;y/U]ԋ$Fal1*"Jk7qu~-^#bD 4j:I6V+c F+a;*En!iՊ"6{7h-re exactly one proposition from each subset must hold. We show that tractable sub-classes of propositional linear temporal logic can be developed, based on the use of underlying XOR sets. We show that such fragments can be decided, tractably, via clausal temporal resolution. We establish completeness and complexity (of the resolution method), and give an example of its usage. This new approach to temporal reasoning provides a framework in which tractable temporal logics can be engineered by intelligently combining appropriate XOR sets. "####