A Temporal Description Logic for Reasoning about Actions and Plans
  A class of interval-based temporal languages for uniformly representing and
reasoning about actions and plans is presented. Actions are represented by
describing what is true while the action itself is occurring, and plans are
constructed by temporally relating actions and world states. The temporal
languages are members of the family of Description Logics, which are
characterized by high expressivity combined with good computational properties.
The subsumption problem for a class of temporal Description Logics is
investigated and sound and complete decision procedures are given. The basic
language TL-F is considered first: it is the composition of a temporal logic TL
-- able to express interval temporal networks -- together with the non-temporal
logic F -- a Feature Description Logic. It is proven that subsumption in this
language is an NP-complete problem. Then it is shown how to reason with the
more expressive languages TLU-FU and TL-ALCF. The former adds disjunction both
at the temporal and non-temporal sides of the language, the latter extends the
non-temporal side with set-valued features (i.e., roles) and a propositionally
complete language.
