In this paper, we study synthesis from logical specifications over finite traces expressed in LTLf and its extension LDLf. Specifically, in this form of synthesis, propositions are partitionedin controllable and uncontrollable ones, and the synthesis task consists of setting the controllable propositions over time so that, in spite of how the value of the uncontrollable ones changes, the specification is fulfilled. Conditional planning in presence of declarative and procedural trajectory constraints is a special case of this form of synthesis. We characterize the problem computationally as 2EXPTIME-complete and present a sound and complete synthesis technique based on DFA (reachability) games.

We define a notion of bounded action theory in the situation calculus, where the theory entails that in all situations, the number of ground fluent atoms is bounded by a constant. Such theories can still have an infinite domain and an infinite set of states. We argue that such theories are fairly common in applications, either because facts do not persist indefinitely or because one eventually forgets some facts, as one learns new ones. We discuss various ways of obtaining bounded action theories. The main result of the paper is that verification of an expressive class of first-order $\mu$-calculus temporal properties in such theories is in fact decidable. This paper is an abridged version of a paper appeared in KR'12.

We investigate an extension of Description Logics (DL) with higher-order capabilities, based on Henkin-style semantics. Our study starts from the observation that the various possibilities of adding higher-order con- structs to a DL form a spectrum of increasing expres- sive power, including domain metamodeling, i.e., using concepts and roles as predicate arguments. We argue that higher-order features of this type are sufficiently rich and powerful for the modeling requirements aris- ing in many relevant situations, and therefore we carry out an investigation of the computational complexity of satisfiability and conjunctive query answering in DLs extended with such higher-order features. In particular, we show that adding domain metamodeling capabilities to SHIQ (the core of OWL 2) has no impact on the complexity of the various reasoning tasks. This is also true for DL-LiteR (the core of OWL 2 QL) under suit- able restrictions on the queries.