1. Structured Analysis Methods and Tools
M. M. Pickard, PhD.
Department of Computer Science

2. Overview
Methods
Tools

3. Structured Analysis Methods
Data Models
Information Flow Models
Functional Models
Behavior Models

4. Structured Analysis Tools
Data Models
Entity Relationship Diagrams
Data Dictionary
Information Models and Functional Models
Data Flow Diagrams
Control Flow Diagrams
Ward and Mellor Extensions
Hatley and Pirbhai Extensions

5. Structured Analysis Tools
Behavioral Models
Process Descriptions

6. Entity Relationship Diagrams
Used to show the relationship between data entities
Cardinality
relative numbers of data entities
Modality
whether data entity is required in the relationship

7. Data Dictionary
Purpose?

8. Data Dictionary Purpose? Often supported by CASE tool
To define and describe all data elements
To serve as a central repository of information about the system’s data
To organize information about contents of data flows, data stores, and, possibly, external entities and processes.
Often supported by CASE tool

9. Data Dictionary Data element documentation
name
aliases
type
length
output format
acceptable values
formula
Source
security
user
comments

10. Data Dictionary (possible components)
Data flow information
Data store information
Process information
External entity information
Data structure information

11. Data Flow Diagram (DFD)
Shows how data moves through an information system.
Logical model
What the system does, not how it does it
Does NOT show program logic
Does NOT explicitly show processing sequence

12. DFD Methods
Gane and Sarson
Yourdon

13. DFD Symbols - Yourdon
Process
Data Flow
Data Store
External Entity

14. DFD - Symbols (Gane & Sarson)
Process
Data Flow
Data Store
External Entity

15. DFD Process Symbol
Receives input data and produces output that has a different content or form.
Process name: verb followed by a singular noun, optional adjective.
Create invoice

16. DFD Data Flow Symbol
A path for data to move from one part of the system to another.
Data flow name: noun and optional adjective.
invoice

17. DFD Process Symbol rules
A process symbol must have at least one input symbol AND one output symbol.
A process symbol can have more than one input symbol and more than one output symbol.
A process can connect any other symbol.

18. DFD Data Flow Symbol rules
A data flow must have a process symbol on at least one end.
Avoid:

19. Process/Data Flow Mistakes
Spontaneous generation (miracle)
Black hole
Create invoice
invoice
Hours worked
Calc. Gross pay
Pay rate

20. Process/Data Flow Mistakes
Gray hole (insufficient input information to create output)
Calc. Gross pay
Date of birth
Gross pay
Pay rate

21. DFD - Data Store
Used to represent a situation when data must be retained in order for a process to use it later.
Data store name: plural name consisting of noun and optional adjectives
Freshmen

22. DFD - External Entity
A person, department, outside organization, or other information system that provides data or receives output from the system.
External entity name: a singular noun
bank

23. Control Flow Diagram Similar to DFD
Shows control flow, not information flow
May link to CSPEC
State Transition Diagram (STD)
Process Activation Table (PAT)

24. Process Description Tools and Methods
Structured English
Decision Tables
Decision Trees

25. Process Description Tools and Methods
Structured English
Based on three building blocks of structured programming and design

26. Process Description Tools and Methods
Structured English
Based on three building blocks of structured programming and design:
sequence, selection, iteration
Uses indentation for readability and to indicate logical hierarchy
Standard, limited vocabulary

27. Process Description Tools and Methods
Decision (Logic) Tables
Used to show complex logic
Tables have four quadrants
Condition stubs
Condition entries
Action stubs
Action entries
A “rule” is a single column

28. Process Description Tools and Methods
Decision (Logic) Tables
Simplification
Rules having the same outcome, but differing by one condition may be combined. Use a dash to replace the differing condition.
Rules that have mutually exclusive conditions (cannot occur) may be carefully eliminated.
Linkage
The final action of a rule may send us to another table.

29. Process Description Tools and Methods
Decision Trees
Effective way to present a combination of simple decisions

30. Summary Entity Relationship Diagrams Data Flow Diagrams
Control Flow Diagrams
Data Dictionary
Process Descriptions