Abstract : In this paper we examine three modal languages that have been proposed in the model-theoretic syntax literature for describing finite ordered trees. We compare their expressive power, and then examine a key complexity-theoretic issue: how expensive is it to decide --- given a theory specifying a certain class of trees --- whether a formula describes a model? Our main result is that for two of these languages this problem is EXPTIME-complete.
Patrick Blackburn, Bertrand Gaiffe, Maarten Marx. Variable free reasoning on finite trees. Proceedings of Mathematics of Language - MOL-8, Jun 2003, Bloomington, Indiana, USA. ⟨inria-00099716⟩