1. Structured Analysis

2. Structured Analysis Graphic, easy to understand
Partitioned process, clear picture of progression from general to specific
Logical rather than physical
Precise, concise and highly readable

3. Tools of structured analysis
Data Flow Diagram
Data Dictionary
Structured English
Decision Tree
Decision Table

4. Data Flow Diagram
A DFD is graphical representation which shows the ‘FLOW OF DATA’.
It is used for the visualization of data processing for structured design.
It shows interaction between the system and outside entity.
It is also called bubble chart.
It is starting point in the system design that decomposes to lowest level.
It consist of series of bubbles joined by lines. Bubbles represents transformations.

5. DFD It has four symbols 1. External Entity 2. Data Flow 3. Data Store
4. Process

6. Explation of symbols of DFD
The EXTERNAL ENTITY symbol represents source of data to the system. External entities determine system boundaries. They are beyond the area of influence of the developer.
The DATA FLOW represents movement of data. Data flow represents ‘DATA IN MOTION’. Data flows are always named. Names should be some identifying noun. For example: order, payment etc.

7. Explanation of symbols of DFD
The DATA STORE symbol represents data that is not moving. Data stores are repository of for data. It is an ‘inventory’ of data. Data stores are named with an appropriate name. For example: Customers, Orders, Products.
The PROCESS symbol represents an activity that transforms or manipulates the data. Processes are actions performed on incoming data flows to produce outgoing data flows. All processes must have some inputs and outputs. Major functions of processes are making decisions.
Input
Process
Output

8. Advantages of DFD
Understanding interestedness of systems and sub systems.
Communicating current system knowledge to the user.
Part of system documentation files.
Logic underlining.
Easy to follow errors.

9. Disadvantages of DFD Physical consideration neglected.
Large number of alteration.
Ambiguous.

10. Data Dictionary Data Element
DD is structured repository of data. It keeps the details of data flows, process and data stores. It documents the list of contents of all data flows.
It has three classes:-
Data Element
Data
structure
Data
Flow
Data
Store

11. Data Dictionary Classes of DD are:-
1. Data elements: smallest unit of data further cannot be decomposed.
2. Data structure: group of data elements.
3. Data Flows and Data Stores: Data flows are data structures in motion. Data stores are data structures in store.

12. Advantages of Data Dictionary
Valuable reference
Improves communication
Compare data description
Cross reference
Build database
Disadvantage is that it do not provide details

13. Structured English
It uses logical constructs to carry out instructions for data (actions)
Decisions are made through the use of IF, THEN, ELSE and SO statements.
It is highly correlated to the decision tree.

14. Example Structured English version of the sales promotion policy:-
IF customer is a preferred customer , and
IF customer orders more than $1000, THEN
apply a 5% discount, and IF customer uses our charge card, THEN apply an additional 5% discount ELSE award $25 bonus coupon ELSE award $5 bonus coupon.

15. 5% DISCOUNT AND AN ADDITIONAL 5% DISCOUNT
Decision Trees
They sketch out logical structure based on some criteria. It is a graphical representations of the conditions, actions and rules found in a decision tree.
DIAGRAMATIC REPRESENTATION
CUSTOMER?
PREFERRED
ORDER MORE THAN $1000?
USED OUR CHARGE CARD ?
$25 BONUS COUPON NO
$5 BONUS COUPON
5% DISCOUNT AND AN ADDITIONAL 5% DISCOUNT
5% DISCOUNT

16. Advantages of decision tree
Easy to understand
Business rues are mapped easily
Real problems solved
No prior assumptions
Process both numerical and categorical data

17. Disadvantages of decision tree
Output attribute must be categorical
Limited to one output attribute only
Decision tree algorithms are unstable
complex

18. Decision Table
It is single representation of the relationship between conditions and actions.
A condition is usually given a value of ‘Y’ for ‘YES’, it is true, ‘N’ for ‘NO’ and a dash for ‘DO NOT CARE’.
Decision tree fails to tell us what conditions to test, a decision table can carry out the conditions to test.

19. Features of decision table
Defines problem and actions
Relationship between condition and action
Two parts :- (1) stub (2) entry
Stub has two parts:- (a) condition stub (b) action stub
Entry has two parts (a) condition entry (b) action entry

20. Decision table diagram
Condition Stub Condition Entry Preferred customer Y Y Y Y N N N N Ordered more than $1000 Y Y N N Y Y N N Used our charge card Y N Y N Y N Y N 5% discount x x Additional 5% discount x $ 25 bonus coupon x $5 bonus coupon x x x x x Action stub Action entry

21. Advantages of decision table
Concise description of logically complex situation
Easier to draw and change than flow charts
Easier to follow a particular path down one column than through several flow charts pages
Limitation
large decision tables can become difficult to modify