S88 is a standard that was approved by the Instrument Society of America (ISA) in 1995 and is in the process of being adopted as an IEC standard. It establishes a framework for the specification of requirements for batch process control, and for their subsequent translation into application software. The framework consists of a variety of definitions, models and structures. This paper outlines some of the models and the relationships between them, and identifies several key issues. It presents a methodology for decomposition of functional requirements in terms of S88 models and structures. Also provided are a number of heuristics (shown in italic print) for the application of the methodology. These heuristics were developed, initially by consideration of the examples in the draft standard but latterly, by applying the methodology to industrial plant. The paper will be of interest to persons involved in batch process control, either in articulating user requirements, defining functional specifications, developing application software or in designing system software. For an introduction to computer controlled batch processing, the reader is referred to the IChemE guide by Sawyer(1). A more comprehensive treatment is provided in the text by Fisher(2). For a more detailed appreciation of S88 the reader is referred to the standard itself(3).