Temporal query languages expressive power: /spl mu/TL vs. T-WHILE

We investigate the expressive power of implicit temporal query languages. The initial motivation was refining the results of (S. Abiteboul et al., 1999) and enrich them with comparison to /spl mu/TL (M.Y. Vardi, 1988). Thus, we address two classes of temporal query languages: /spl mu/TL-like languages based on TL and T-WHILE-like languages based on WHILE. We provide a two-level hierarchy (w.r t. expressive power) for these temporal query languages. One of the contributions solves an open problem: the relative expressivity of /spl mu/TL and T-FIXPOINT.