Structured Systems Analysis

Structured Systems Analysis

Use of graphics to specify software Important technique of the 1970s A few popular techniques Structures system analysis — A nine-step technique to analyze client’s needs  

Step-wise refinement is used in many of steps Step 1: Draw the Data Flow Diagram (DFD)

 A pictorial representation of all aspects of the logical data flow Logical data flow — What happens

·        Physical data flow — How it happens

·        Any non-trivial product contains many elements

·        DFD is developed by stepwise refinement

·        For large products a hierarchy of DFDs instead of one DFD

·        Constructed by identifying data flows: Within requirements

Petri nets — Formal technique for describing concurrent interrelated activities

Invented by Carl Adam Petri, 1962 Consists of four parts

(1)             A set of places

(2)             A set of transitions

(3)             An input function

(4)             An output function

Originally of interest to automata theorists

Found wide applicability in computer science

Performance evaluation

Operating systems

Software engineering