Formal Specification and Design Techniques

Type of specification

• Informal:
• Free form, natural language
• Ambiguity and lack of organization can lead to incompleteness, inconsistency, and misunderstandings

Type of specification

• Formal:
• » Syntax and semantics rigorously defined
• » Precise form, perhaps mathematical
• » Eliminate imprecision and ambiguity
• » Provide basis for mathematically verifying equivalence between specification and implementation
• » May be hard to read without training

Static aspect of a system

• In Z, schemas are used to describe both static and dynamic aspects of a system. The static aspects Include:
• the states of a system can occupy;
• the invariant relationships that are maintained as the system moves from state to state.

Dynamic aspects of system

• The dynamic aspects include:
• the operations that are possible;
• the relationship between their inputs and outputs;
• the changes of state that happen.

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