Tools of Structured Analysis, Lecture notes of System Analysis and Design

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The Tools of Structured Analysis

Chapter-

Structured Analysis

Analysts use various tools to understand and describe the information system. One of the ways is using structured analysis. What is Structured Analysis?  (^) Structured Analysis is a development method that allows the analyst to understand the system and its activities in a logical way.  (^) It is a systematic approach, which uses graphical tools that analyze and refine the objectives of an existing system and develop a new system specification which can be easily understandable by user.

Structured Analysis Tools

During Structured Analysis, various tools and techniques are used for system development. They are −  (^) Data Flow Diagrams  (^) Data Dictionary  (^) Decision Trees  (^) Decision Tables  (^) Structured English  (^) Pseudo code

Block Diagram of Information Gathering Tools

Basic Elements of DFD

• (^) DFD is easy to understand and quite effective when the required design is not clear and the user wants a notational language for communication. However, it requires a large number of iterations for obtaining the most accurate and complete solution.
• (^) The following table shows the symbols used in designing a DFD and their significance −

Symbol Name Symbol Meaning Square Source or Destination of Data Arrow Data flow Circle Process transforming data flow Open Rectangle Data Store

Context Diagram

 (^) A context diagram helps in understanding the entire system by one DFD which gives the overview of a system. It starts with mentioning major processes with little details and then goes onto giving more details of the processes with the top-down approach.  (^) The context diagram of mess management is shown in the following slide

Context Diagram of A Mess Management System

Sl. No. Data Name Description No. of Characters 1 ISBN ISBN Number 10 2 TITLE title 60 3 SUB Book Subjects 80 4 ANAME Author Name 15

Decision Trees

 (^) Decision trees are a method for defining complex relationships by describing decisions and avoiding the problems in communication. A decision tree is a diagram that shows alternative actions and conditions within horizontal tree framework. Thus, it depicts which conditions to consider first, second, and so on.  (^) Decision trees depict the relationship of each condition and their permissible actions. A square node indicates an action and a circle indicates a condition. It forces analysts to consider the sequence of decisions and identifies the actual decision that must be made.

Discount policy Bookstore Libraries or individuals 6 or more Less than 6 50 0r more 20- 6- Less than 6 25% Nil 15% 10% 5% Nil Types of customer Size of order (^) Discount

Drawbacks of Decision Tree

The major limitation of a decision tree is that it lacks information in its format to describe what other combinations of conditions you can take for testing. It is a single representation of the relationships between conditions and actions.

Components of a Decision Table

 (^) Condition Stub − It is in the upper left quadrant which lists all the condition to be checked.  (^) Action Stub − It is in the lower left quadrant which outlines all the action to be carried out to meet such condition.  (^) Condition Entry − It is in upper right quadrant which provides answers to questions asked in condition stub quadrant.  (^) Action Entry − It is in lower right quadrant which indicates the appropriate action resulting from the answers to the conditions in the condition entry quadrant.

IF (Condi tions) Customer is a bookstore? Y Y N N N N Order-size 6 copies or more? Y N N N N N Customer librarian or individual? Y Y Y Y Order size 50 copies or more? Y N N N Order size 20-49 copies? Y N N Order size 6-19 copies? Y N Then( Action ) Allow 25%discount * Allow 15% discount * Allow 10%discount * Allow 5%discount * No discount allowed * *