Current research in specifications is emphasizing the practical use of formal specifications in program design. One way to encourage their use in practice is to provide specification languages that are accessible to both designers and programmers. With this goal in mind, the Larch family of formal specification languages has evolved to support a two-tiered approach to writing specifications. This approach separates the specification of state transformations and programming language dependen-cies from the specification of underlying abstractions. Thus, each member of the Larch family has a subset derived from a programming language and another subset independent of any programming languages. We call the former interface languages, and the latter the Larch Shared Language. This paper focuses on Larch interface language specifications. Through examples, we illustrate some salient features of Larch/CLU, a Larch interface language for the programming language CLU. We give an example of writing an interface specification following the two-tiered approach and discuss in detail issues involved in writing interface specifications and their interaction with their Shared Language components.

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. This guide is for authors who are preparing papers for Formal Aspects of Computing using the L a T E X document preparation system and the FAC style file. 1. Introduction In addition to the standard submission of hard-copy from authors, Formal Aspects of Computing accepts machine-readable forms of papers in L a T E X. The layout design for Formal Aspects of Computing has been implemented as a L a T E X style file. The FAC style is based on the ARTICLE style as discussed in the L a T E X manual [Lam86]. Commands which differ from the standard L a T E X interface, or which are provided in addition to the standard interface, are explained in this guide. This guide is not a substitute for the L a T E X manual itself. Authors planning to submit their papers in L a T E X are advised to use fac.sty as early as possible in the creation of their files. 1.1. Introduction to L a T E X L a T E X is constructed as a series of macros on top of the T E X typesetting program. L a...