CS636 Highlighted Slides Week 8-16 by Masooma

Intoduction to Specification in VDM-SL

At the end of this chapter you should be able to:

• write a formal specification of a system in VDM-SL
• correlate the components of a UML class diagram with those of a VDM specification
• declare constants and specify functions to enhance the specification
• explain the use of a state invariant to place a global constraint on the system
• explain the purpose of the nil value in VDM

The Case Study: Requirements Analysis

• The example we will use throughout this chapter will be that of an incubator, the temperature of which needs to be carefully controlled and monitored in order to provide the correct conditions for a particular biological experiment to be undertaken.
• We will specify the software needed to monitor and control the incubator temperature.

An incubator is a device used to maintain a controlled environment—especially temperature—which is crucial in biological experiments. The aim is to ensure that the temperature inside the incubator is accurate and stable.

• In developing any software system the first stage in the process involves an analysis of the system and an initial statement of the requirements.
• It is very important, in any requirements definition, to be clear about the system boundaries, and we should make it clear here that in this initial version, control of the hardware lies outside of our system.
• In other words, for the time being we will be specifying a system that simply monitors the temperature of the incubator.