Since its inception in 1991, the Temporal Agent Model theory (TAM) has undergone a number of changes; some of these changes have been minor (such as a change in the style of semantic presentation) and some have been more major (such as the addition or subtraction of programming constructs from the TAM language). Throughout these changes however, the computational model underlying the theory has remained constant, allowing for a comparison of different flavours of the language. This has proved a fruitful area of research, but has also meant that references to the TAM theory may be ambiguous. In this paper we present a standard TAM theory, including a language syntax, semantics, and refinement calculus, and propose that this standard be used in future TAM projects. We also discuss refinement hueristics for ensuring implementable programs. 1 Introduction In January 1992 the first version of TAM was presented at the Nijmegen workshop on the formal development of real-time and fault tolera..