Integrating Z into Large Projects Tools and Techniques

Overview This paper addresses the problem of using Z to specify large software intensive systems. It is addressed particularly at safety, security or business-critical systems that require a rich language like Z to specify complex data and behaviour. Examples of such systems include air traffic control [1] and financial systems [2]. I am particularly concerned here with the process of writing a system specification. I have claimed [3] that this process is beneficial in itself regardless of any subsequent analysis or proof. The benefits are not automatic, however. The specification is only useful if 1. it is written as part of the requirements elicitation and analysis process; 2. it is comprehensible to all the stakeholders; 3. it is grounded in the application domain; 4. it expresses all the concepts that are relevant; 5. it is integrated into the rest of the development and verification process. On a purely practical level, this implies that we want Z to be part of the ordinary documents that are used every day on the project. That means, in practice, that it has to be integrated into Microsoft Word. So I first describe a tool for writing and checking Z within the Word environment. That is only the start, however: we also need a process for writing the specification and guidelines for its structure. I will describe some progress we have made towards these goals.