We present a framework for obtaining effective characterizations of simple fragments of future temporal logic (LTL) with the natural numbers as time domain. The framework is based on a form of strongly unambiguous automata, also known as prophetic automata or complete unambiguous Büchi automata and referred to as Carton-Michel automata in this paper. These automata enjoy strong structural properties, in particular, they separate the "finitary fraction" of a regular language of infinite words from its "infinitary fraction" in a natural fashion. Within our framework, we provide characterizations of several natural fragments of temporal logic, where, in some cases, no effective characterization had been known previously, and give lower and upper bounds for their computational complexity.

Comment: 22 pages, to appear in LMCS Special Issue: Selected papers of the conference on "Foundations of Software Science and Computation Structures":
FOSSACS 2012

• 03B44 - Temporal logic
• 03D05 - Automata and formal grammars in connection with logical questions