Method integration for real-time software design

Although formal methods have been around for a number of years, their industrial take-up can be described at its best as poor. Some of the reasons have for this include: 1) problems in finding the right level of abstraction, 2) lack of user education, 3) hard to write a "good" specification, 4) difficult to understand, 5) absence of structure and method. Possible solutions could be: 1) create easier to use formal methods, 2) better education, 3) integrate formal methods with other methods (i.e. structured methods). The first has obviously been tried, judging from the amount of formal methods available. The second is of continuing focus in education establishments. The third is of most interest in the paper. Looking at structured design methods for real time software design, we note that they have had good take-up in industry, but generally lack the attributes that formal methods are specifically designed for. Structured methods have no rigorous definition of the structures that they employ, and little or no property verification facilities. The paper looks at integrating formal and structured methods for real time design and verification. More specifically we describe a case study integrating the diagrammatic formalism Modecharts and the structured design method HRT-HOOD, using the timed automata tool Uppaal for model checking properties of the HRT-HOOD design. One of the results of this approach is that the abstraction that the structured method brings, can be used to limit the state space when model checking a particular property, and so in many cases avoid the state space explosion.