Structured system analysis and design

STRUCTURED SYSTEM
ANALYSIS AND DESIGN
CHP 5. STRCTURED SYSTEM ANALYSIS TOOLS AND TECHNIQUES
MR. JAYANT. P. DALVI

FUNCTIONAL DECOMPOSITION DIAGRAM
• an analytical tool used to represent the various functions of the
system and its decomposition up to the lowest level/function.
• It is diagrammatic representation in hierarchal format of the system.
• Each function is numbered using level numbering convention.
Diagrammatically it has inverted tree like structure.

E-R DIAGRAM
• E-R Model means entity relationship model represents conceptual way of data modeling.
• For every business system conceptual modeling is the intermediate phase that leads to
physical data base design. First step of conceptual data modeling is semantic analysis which
focuses on entities and their relationships. Some important basic concepts fordrawing E-
Diagrams are as follows.
1. Entity: - An entity is an object that has its own unique identity.
For example: Any car, book, person, dream.[Important: Entity can be concrete or abstract.]
2. Attribute: - An attribute is an aspect, characteristic or quality of either an entity or
relationship. For example: color, size shape of a car can be the attributes.
3. Relationship: - A relationship is a meaningful association, linkage or connection between
entities.
4. Entity set: - Entity set is a set of entities of same kind. For example: Accounts holder of same
bank can form an entity set.
5. Relationship set:- A relationship set is collection of relations of same type.

ER DIAGRAM
• Technically if a relationship set contains a
primary key it is called a strong entity set
otherwise it is called weak entity set.
• An entity may appear in
I One- one relationship
II One – many relationship
III Many –many relationship (m-n)
• 1] One- one relationship: (1:1) For a given
occurrence of an entity there is exactly one
occurrence of another entity.
• For example: - Any one employee of an
organization is identified by identity card.

ER DIAGRAM
2] One - many relationships: (1:
M) For a given (value) occurrence
of any entity there can be more
than one (value) occurrences of
another entity.
For example: A branch of bank has
much number of customers. So it
is 1-m relationship.

ER DIAGRAM
3] Many to many relationship:
(m:n) There can be multiple
occurrences of both the entities
that are being related
• For example: Subjects opted by
students for a particular course.

DATA FLOW DIAGRAM-DFD
• Data flow diagram represents flow of data through system.
• DFD is a graphic tool which defines input , output and processes of
the system.
• It helps analyst to explain his understanding of the system to user.
• Symbols used:- Different symbols represent different system
elements. But use of symbol associated with each element depends
upon which approach is used.
• There two types of popular symbol ling styles.

DFD
• Rules For Constructing Data Flow Diagrams
1. Procedures should be named and numbered for easy reference.
2. Process should be numbered if exploded into lower level.
3. Names of data sources, destination &stores should be in capital
letters.
4. Process and data flow names should have first letter capital.
5. The direction of flow is from left to right and top to
bottom.Traditional flow of data is from source (upper left corner ) to
the destination (lower right corner)

DFD
• do’ s and dont’s in data flow diagram:
Dataflow should reflect the data not the documents on which it resides
Process name should fully describe the action taking place and should be able to explain inflows &
out flows of the data.
Avoid usage of vague names to the activity such as Review, Handle.
Assign unique process names to the activity.
Data stores should represent logical names indicating what kind of data is stored.
Don’t assign program specific names like STUDENT.DBF to document names.
No new entity or data store at any level which does not papers at a level previous to that level.
No data flow should cross over through all the levels in the DFD.

Important guide lines for data stores and entities:
• Data stores mainly are of two types
1. Master
2. Transaction.
Data store should have only related data stored in them.
All data stores appearing at the first level should also appear at lower levels.
Entities which get repeated right from context level to the lower levels are shown by
Data stores which are used to access stored data more than once are shown by

DFD
• Data flows going onto a
process and coming out of a
process should have different
names
For example
Verify student’s details
• Students –mast student
details verified student’s
details

DFD
• Guide lines for drawing context level (0th level diagram)
a) It contains and represents single process and determines the
boundary of the
system.
b) Name of the process usually represents the name of the system.
c) All entities are shown at context level and should remain the same
(even the name )through all the level.

• Case Study:
• Draw context level, first level for
following system. A star
company procures the
materialagainst the requisition
received from stores. Purchase
department prepares a purchase
order and sends a copy of it to
stores for ready reference.
Stores department receives the
material from the vendor and
prepares GRN [goods receipt
note].Stores department
updates the stock of the items
for the accepted quantity
mentioned in GRN.

CASE STUDY
• the public relation department is one of the most important
department of the ICT faculty. In order to advertise the ICT program
to public, we need the software to support our staff in the process of
road show scheduling. So, PR staff can use the system to arrange,
assign works and update schedule on Google calendar.
• Moreover, the software must provide all important data and
summary report document .

Structured system analysis and design

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