Activities of Formal Methods The main activities of Formal methods are, Writing a formal specification Proving properties about the specification Constructing a program by mathematically manipulating the specification Verifying a program by mathematical argument

Key points Formal system specification complements informal specification techniques Formal specifications are precise and unambiguous. They remove areas of doubt in a specification Formal specifications force an analysis of the system requirements at an early stage. That helps us in correcting errors at this stage is cheaper than modifying a delivered system

Key points Formal specification techniques are most applicable in the development of critical systems and standards. Algebraic techniques are suited to interface specification where the interface is defined as a set of object classes Model-based techniques model the system using sets and functions. This simplifies some types of behavioural specification

7 Myths of Formal Methods Anthony Hall – IEEE Software Sept. 1990 Formal methods can guarantee that software is perfect. They work by proving that programs are correct. Only highly critical systems benefit from their use. They involve complex mathematics. They increase the cost of development. They are incomprehensible to clients. Nobody uses them for real projects.

Limitations to Formal Methods Use formal methods as supplements to quality assurance methods not a replacement for them Useful for consistency checks, but formal methods cannot guarantee the completeness of a specifications Formal methods must be fully integrated with domain knowledge to achieve positive results

Acceptance of formal methods Formal methods have not become mainstream software development techniques as was once predicted Other software engineering techniques with better quality results. Time-to-market versus high quality Hard to scale up to large systems Not well-suited for specifying and analysing user interfaces and user interaction