PROTEIN (PROver with a Theory Extension INterface) is a PTTPbased first order theorem prover over built-in theories. Besides various standardrefinements known for model elimination, PROTEIN also offers a variant of model elimination for case-based reasoning and which does not need contrapositives.

Theory Reasoning means to build-in certain knowledge about a problem domain into a deduction system or calculus, which is in our case model elimination. Several versions of theory model elimination (TME) calculi are presented and proven complete: on the one hand we have highly restricted versions of total and partial TME. These restrictions allow (1) to keep fewer path literals in extension steps than in related calculi, and (2) discard proof attempts with multiple occurrences of literals along a path (i.e. regularity holds). On the other hand, we obtain by small modifications to TME versions which do not need contrapositives (a la Near-Horn Prolog). We show that regularity can be adapted for these versions. The independence of the goal computation rule holds for all variants. Comparative runtime results for our PTTP-implementations are supplied. 1 Introduction The model elimination calculus (ME calculus) has been developed already in the early days of automated theorem proving [Lovel...

The following list of tableaux-based theorem provers was assembled in the Spring and Summer 1993 as the result of a wide-spread enquiry via e-mail. It is intended to provide a short overview of the field and existing implementations. For each system, a short description is given. Additionally, useful information about the system is presented in tabular form. This includes the type of logic which can be handled by the system (input), the implementation language, hardware and operating systems requirements (implementation). Most of the systems are available as binaries or as sources with documentation and can be obtained via anonymous ftp or upon request. The descriptions and further information have been submitted by the individuals whose names are given as contact address (except for 12, 14, 21 which have been formulated by the editor on the basis of submitted texts). The provers are ordered alphabetically by their name (or the author's name). 1 1 3 T A P " 3 T A P [...