Summary: On TLA as a Logic
Mart'in Abadi 1 and Stephan Merz 2
1 Digital Equipment Corporation, Systems Research Center, 130 Lytton Avenue,
Palo Alto, CA 94301, U.S.A.
2 Institut f¨ur Informatik, TU M¨unchen, Arcisstr. 21, 80290 M¨unchen, Germany
Summary. We describe the Temporal Logic of Actions (TLA) from a logical per
spective. After giving the syntax and semantics of TLA, we discuss some methods
for representing reactive systems in TLA and study verification rules.
1 The L in TLA
The Temporal Logic of Actions (TLA) is a variant of temporal logic, de
signed for the specification and verification of reactive systems in terms of
their actions. In this paper we describe TLA from a logical perspective; our
description of TLA has three aspects:
1. As a logic, TLA has a precise syntax and semantics. We define these in
the next section. Our intent is not to develop a new TLA, but rather to
explain and to refine Lamport's definition of TLA .
2. Like HOL  and other logics, TLA can serve for representing reac
tive systems in several styles. In particular, a specification may describe
concurrent steps as interleaved or simultaneous; communication between
components may be synchronous or asynchronous. We discuss a few styles