2.3 PDL-based requirements definition

• Requirements may be defined operationally using a language like a programming language but with more flexibility of expression
• Most appropriate in two situations
  • Where an operation is specified as a sequence of actions and the order is important
  • When hardware and software interfaces have to be specified

• Disadvantages are
  • The PDL may not be sufficiently expressive to define domain concepts
  • The specification may be taken as a design rather than a specification