1. Tools for Structured Design
Organized By: Vinay Arora
Assistant Professor
CSED, Thapar University
www.slideshare.net/aroravinay
2. Disclaimer
This is NOT A COPYRIGHT MATERIAL
Content has been taken mainly from the following books:
System Analysis and Design Methods By Jeffrey L Whitten & Lonnie D Bentley ,
Analysis & Design of Information Systems By James A. Senn,
System Analysis & Design By Elias M. Awad,
Modern System Analysis & Design By Jeffrey A. Hoffer, Joey F.George & Joseph
S. Valacich
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3. Tools for Structured Analysis
For the Business System under Investigation DECISION &
PROCEDURES are Important to System Analyst.
Various TOOLS are present for Studying Operational Procedures and
Decision Making Steps.
TOOL – A Device, Object or Operation used to accomplish a Specific
Task.
Three TOOLS for Documenting Procedures:
Decision Tree, Decision Table and Structured English
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4. Structured English
STRUCTURED ENGLISH is the use of the English Language with the
SYNTAX of Structured Programming.
STRUCTURED ENGLISH aims at getting the benefits of both the
Programming Logic and Natural Language.
Program Logic helps to attain precision while natural language helps in
getting the convenience of spoken Languages.
Method to Overcome Problem of AMBIGUOUS Language.
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5. Guidelines when writing Structured
English
Statements should be Clear and Unambiguous
Use One Line per Logical Element
All LOGIC should be expressed in Operational, Conditional and
Repetition Blocks
Logical Blocks should be indented to show Relationship
Keywords should be Capitalized
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7. Common Keywords
START, BEGIN, END, STOP, DO, WHILE, DO WHILE, FOR,
UNTIL, DO UNTIL, REPEAT, END WHILE, END UNTIL, END
REPEAT, IF, IF THEN, ELSE, IF ELSE, END IF, THEN, ELSE
THEN, ELSE IF, CASE, EQUAL, TRUE, FALSE, AND, OR, XOR
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8. Developing Structured Statements
Structured English uses THREE Basic Types of Statements to describe a
PROCESS:
SEQUENCE STRUCTURES
DECISION STRUCTURE
ITERATION STRUCTURES
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9. Sequence Structures
A Single Step or Action Included in a Process.
None of the Steps contains a Decision or any Conditions that determine
whether the steps are taken.
Operation Statements written as ENGLISH PHRASES executed from
the top down.
Example:
1). Pick Out a Desirable Book
2). Take the Book to the Checkout Counter
3). Pay for the Book
4). Obtain a Receipt
5). Leave the Store
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10. Decision Structure
Another way of Showing Decision Analysis.
Decision Structures occur When TWO or MORE Actions can be taken,
depending on the value for a Specific Condition.
After Decision Making Stated Actions or Sets of Actions for that
Condition will be taken.
Once Condition is made, ACTIONS are Unconditional.
Keywords Like IF/THEN/OTHERWISE are used.
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11. Example
IF a desirable book is found, THEN
Take the book to the checkout counter.
Pay for the book.
Be sure to obtain a receipt.
Leave the store.
OTHERWISE
Do not take the books to the checkout counter.
Leave the Store.
END IF
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12. Iteration Structure
Iteration Instructions permit Analyst to Describe the cases where:
Certain Activities are repeated WHILE a certain Condition Exists
OR
UNTIL a Condition Occurs
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13. Example
DO WHILE Still examining more books.
Read the title of the Book.
IF the title sounds interesting
THEN pick up the book and thumb through it.
Look at the Price.
IF you decide you want the book
Put it in the DESIRABLE BOOK stack.
ELSE Put it back on the shelf.
END IF
ELSE Continue
END DO
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14. IF Desirable books are found THEN
Take the books to the checkout counter.
Pay for the books.
Be sure to obtain a receipt.
Leave the store.
ELSE
Do not take books to the checkout counter
Leave the store
END IF
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16. Decision Tree
Conditions – Possible States of an ENTITY.
Action – What to do when certain condition/s occur…
Actions are the Alternatives.
Tools used in Understanding & Matching combinations are -
- Decision Trees
- Decision Tables
- Structured English
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17. Decision Tree
Decision Tree – Diagram that presents CONDITIONS and ACTIONS
sequentially.
Shows which CONDITIONS to consider First which Second and so on.
Method of showing the relationship of condition & its permissible
actions.
Diagram resembles branch of a TREE.
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21. Decision Tree (cont.)
Formal Identification of Actual Decision.
Force Analyst to Consider the Sequence of Decisions.
Drawback of Decision Tree – A Large number of branches with many
paths through them will cloud rather than aid analysis.
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30. Decision Table
Decision Table – Matrix of Rows & Columns, rather than a TREE.
Decision Rules are present in Decision Table.
Decision Tables are a Precise yet Compact WAY TO MODEL complicated
logic.
Decision Tables, like If-Then-Else and Switch-Case Statements,
ASSOCIATE CONDITIONS WITH ACTIONS to perform.
Decision Rule – Procedure to follow when certain Conditions Exits.
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33. Decision Tree - Example
Longer than 10 Days Within 10 Days
Over $10000 Below $5000
$5000 to $10000
Pay Full Invoice Amount
Take 2% Discount from Pay Full Invoice Amount
Take 3% Discount from Invoice Total
Invoice Total
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35. Decision Table – Example Payment
Discount
There are various Formats of Decision Tables. Format doesn’t Change
the Usefulness of Decision Table.
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36. Building Decision Table - Steps
1- Determine most relevant factors to consider in making a DECISION.
2- Determine the most feasible steps or activities under varying conditions.
3- Study the Combinations of Conditions that are Possible.
4- Fill in the Table with DECISION Rules.
5- Mark Action entries with ‘X’ to signal action(s).
6- Examine Table for Redundant Rules.
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46. Data Dictionary
DATA DICTIONARY – Can be defined as a CATALOG or a
REPOSITORY of the Elements in a SYSTEM.
To Manage details in a Large System.
To Document the features of a System.
To Communicate a Common Meaning for all System Elements.
Record in DD – Data Element, Data Structure.
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64. DFD – A Tool for data flow analysis
DFD - A Structured, Diagrammatic technique for showing the
functions performed by a System & the data flowing Into, out of &
within it.
Following Data-Oriented Questions about a Target System:
What processing is done?
What data is Needed?
The Context Diagram (Level 0 DFD) is the Highest Level in a Data
Flow Diagram and contains only One Process, representing the ENTIRE
SYSTEM.
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75. DFD Principles
A System can be decomposed into Subsystems and Subsystems can be
decomposed into Lower Level Subsystems and so on.
Each Subsystem represents a Process or Activity in which data is
processed.
At the Lowest Level, Processes can no longer be decomposed.
Just as a System must have Input and Output, so a Process must have
Input and Output.
Data Enters the System from the Environment, Data Flows between
Processes within the System and Data is produced as Output from the
System.
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95. Physical & Logical DFD
WHAT the System does - Current Physical DFD
HOW it does it - Current Logical DFD
WHAT it should do - Required Logical DFD
HOW it should do it - Required Physical DFD
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102. Reference List
1. System Analysis and Design Methods By Jeffrey L Whitten & Lonnie D Bentley
2. Analysis & Design of Information Systems By James A. Senn
3. System Analysis & Design By Elias M. Awad
4. Modern System Analysis & Design By Jeffrey A. Hoffer, Joey F.George & Joseph S. Valacich
5. http://yourdon.com/strucanalysis/wiki/index.php?title=Chapter_9
6. http://www.ehow.com/about_5095247_definition-data-flow-diagrams.html
etc…….
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