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## Friday, February 25, 2011

### How to design conventional components - Graphical Design Notation and Tabular Design Notation

There were some logical constructs developed from which any program could be formed. Each construct has a logical structure. The constructs are sequence, condition, and repetition.
- Sequence implements processing the steps that are essential in the specification of any algorithm.
- Condition provides the facility for selected processing based on some logical occurrence.
- Repetition allows for looping.
Structured programming is a design technique that constrains logic flow to three constructs: sequence, condition and repetition. The structured constructs were supposed to limit the procedural design of software to a small number of predictable operations.

GRAPHICAL DESIGN NOTATION
Activity diagram allows a designer to represent sequence,condition and repetition. Flowchart, like an activity diagram, is quite simple pictorially.
The dogmatic use of only structured constructs can introduce inefficiency when an escape from a set of nested loops or nested conditions is required. Additional complication of all logical tests along the path of escape can hinder the control flow, increase the possibility of error and have a negative impact.
There are two options:
- procedural representation is redesigned so that escape branch is not required at a nested location.
- structured constructs are violated in a controlled manner; that is , a constrained branch out of the nested flow is redesigned.

TABULAR DESIGN NOTATION
Decision tables translates actions and conditions in a tabular form. It is difficult to misinterpret. A decision table is divided into quadrants:
- Upper left quadrant: contains a list of all conditions.
- Lower left quadrant: contains a list of all actions that are possible based on combinations of conditions.
- Right hand quadrant: a matrix that indicates condition combinations and corresponding actions. Each column of matrix may be interpreted as a processing rule.

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