2018/08/31 by Pietro Galliani
Computer Science · Mathematics · #cs.LO #math.LO
paper · pdf · doi:10.4204/eptcs.277.5
published as EPTCS 277, 2018, pp. 58-72 · In Proceedings GandALF 2018, arXiv:1809.02416
arxiv created 2018/09/11 · arxiv updated 2018/09/12
I consider the question of which dependencies are safe for a Team Semantics-based logic FO(D), in the sense that they do not increase its expressive power over sentences when added to it. I show that some dependencies, like totality, non-constancy and non-emptiness, are safe for all logics FO(D), and that other dependencies, like constancy, are not safe for FO(D) for some choices of D despite being strongly first order. I furthermore show that the possibility operator, which holds in a team if and only if its argument holds in some nonempty subteam, can be added to any logic FO(D) without increasing its expressive power over sentences.