3. Management Information System
MIS is a system consisting of people,
machines, procedures, databases and data
models, as its elements.
The system gathers data from the internal
and external sources of a organization,
processes it and supplies information.
4. SSAD was introduced in 1981 as the standard method of
analysis and design developed by CCTA (Central
Computing and Telecommunications Agency) for UK
Government projects
SSAD was made mandatory for all new information
system developments in 1983
HISTORY
5. Structured Systems Analysis and Design (SSAD) is an
integrated set of standards and guides for the analysis and
design of computer systems
It is an integrated set of standards and guidelines consisting
of : Structural standards, which define the structure of a
development project in the form of
explicitly defined tasks, with clearly defined
interfaces between them, and also the tangible
products
Structured Systems Analysis and Design
6. Improves productivity
Improves flexibility
Improves quality by reducing error rates
Delivers the system to users on time
Prevents IT developers’ bureaucracy
Delivers systems that meets user's needs
Benefits Of SSAD
7. Disadvantages Of SSAD
The size of SSAD is a big hindrance to using it in all
circumstances
There is a large investment in cost and time involved in
training people to use the technique to come to terms with
There are lot of standards for the preparation and
presentation of documents
8. Data Flow Diagram
Data Dictionary
Decision Tree
Structured English
Decision Table
Tools of SSAD
9. Data Flow Diagram
Data Flow Diagram is a graphical representation of
the logical flow of the data.
It helps in expressing the system’s requirements in
simple and understandable form
It is also known as a bubble chart.
Its aim is to clarify the system requirements and
identify major transformations that will become
programs in system design
It decomposes the requirement specifications down
to the lowest level of details
10. DFD contains 4 graphic symbols for
Source/destination
Data flow
Process
Data store
12. Sign: Arrow
Symbol:
Meaning: Data Flow
Description : It identifies the data flow;
it is a pipeline through which the data flows.
Data Flow
13. Sign: circle/ bubble
Symbol:
Meaning: Process
Description: It represents a process that
transforms incoming data flow into outgoing
flow.
Process
14. Sign: Rectangle
Symbol:
Meaning: Data store
Description:It represents data store.
Data store
15. Processes should be named and numbered
The direction of flow is from top to bottom from left to
right
The name of the data stores, sources and destination is in
capital letter.
Process and data flows name have the first letter capital
When a process is explored / divided in lower level they
are number properly
Rules for constructing /drawing DFD
16. In case of payroll system to prepare salary statement for each
employee data flow can be represented as-
Employee Data
Accounts Dept
Payroll
processing Salary statement
Employee
file
Employee
17.
18. Though DFD is very effective when required
design is not clear and the user requires only graphic
representation but more than 10-12 processes will
make system complex and difficult to understand.
ADVANTAGE & DISADVANTAGE
19. Data Dictionary
A data dictionary is a structured repository of data. It
is a set of rigorous definitions of all DFD data elements
and data structure
It supports documentation in a better way
It serves as a common database for programmer and
can be also used for control purposes
20. THERE ARE THREE CLASSES OF ITEMS TO BE
DEFINED:
1. Data element -
the smallest unit of data that provides for no further
decomposition.
2. Data structure -
a group of data elements handled as a unit
3. Data flows/stores -
data flows are nothing but data structures in motion,
whereas data stores are data structures at rest.
21. Rules for constructing Data Dictionary
The terms used to describe data structures are always in
capital letters
Assigned names should be straightforward and user
oriented
There should be names for every data flow, data store,
data structure and data element
Consistency checks should be performed
Identification numbers of the process and their names
should be mentioned in the data dictionary
22. STRUCTURED ENGLISH
Structured English aims at getting the benefits of both the
programming logic and natural language
It uses logical construction and imperative sentences
designed to carry out instructions for action
Decision are made through IF-THEN-ELSE
statements
Its sentences should be precise, concise and clear
in word and meaning
23.
24.
25. Example of Structured English
A bank will grant loan under the following
conditions :
If a customer has an account with the bank and
had no loan outstanding, loan will be granted
If a customer has an account with the bank but
some amount is outstanding from previous loans
then loan will be granted if special approval is
given
Reject all loan applications in all other cases
26. IF customer has a Bank Account THEN
IF Customer has no dues from previous account
THEN
Allow loan facility
ELSE
IF Management Approval is obtained THEN
Allow loan facility
ELSE
Reject
27. DECISION TREE
Clear graphic representation of the logic, which looks like
the branches of a tree, called decision tree
Easy to construct, read and update
Turns a decision table into a diagram & is read from left to
right
Can be used to verify logic in problem that involves
few complex decisions.
28. Example: Computer dealer gets a trade discount of 35% if the order size is 6 or
more PCs, whereas for orders from educational institutions and individuals, 15%
discount is allowed on order of 6-19 PCs, 20% on orders for 20-49 PCs; 30% on
orders for 50 PCs or more
Dealer 6 or more 35%
Less than 6 NIL
DISCOUNT POLICY
Educational
Institution or individual 50 or more 30%
20 – 49 20%
6-19 15%
Less than 6 NIL
Decision tree
29.
30. DECISION TABLE
A matrix of rows and columns that shows conditions
and actions
Decision rules state the procedure to be followed
when certain conditions exist.
Decision table are best-suited for dealing with
complex branching routines, e.g., inventory control
A condition is usually given a value of 'Y' for 'Yes,
if is true", 'N' for 'No' and a dash for 'Do not care' in
each rule.
31. Decision table consists of four sections. A condition stub at the
upper left, a condition entry at the upper right, an action stub at the
lower left, and an action entry at the lower right
Questions are listed in the condition stub and the action stub
outlines the action to be taken to meet each condition
Condition entry part contains the answers to
questions asked in the condition stub and the action
entry part indicates the appropriate action
Condition Stub Condition Entry
Action Stub Action Entry
32. In constricting a decision table, the following rules are
observed:
A decision should be given a name to be written at the top left
of the table
The logic should be independent of the sequence in which the
condition rules were written but the action takes place in the
order in which the events occur
Consistent and standardized language should be used
Duplication of the terms should be avoided to the maximum
extent
33.
34. TECHNIQUES OF STRUCTURAL SYSTEM
ANALYSIS AND DESIGN
Data Flow Modeling (DFM)
Logical Data Structure (LDS)
Entity Life History (ELH)
35. DATA FLOW MODELING
Pictorial representations of systems have long
been acknowledged as being more effective than
narrative
Conventional flowcharts have been used for
many years, with considerable advantages over
narrative
Here are some examples:
System flowchart (for high-level system
description)
Clerical procedure flowchart (for low-level
description)
Computer run chart
36. Disadvantages
They confuse the logical aspects of the system (what is
done) with the specific physical implementation (how
it is done)
They do not allow any easy transition from high-level
broad description to detailed low-level description
They are "procedure orientated", placing the greatest
emphasis on procedures in the system, rather than on
data which appears only occasionally on the flow chart
37. LOGICAL DATA STRUCTURE:
The pictorial representation of entities and the
relationships between them is called an Entity
model
A current system Logical Data Structure
(LDS) is a form of Entity model which
represents entities and their relationships in the
current system environment
38.
39. Entities
For those unfamiliar with the term "entity" its
nearest equivalent in more familiar
terminology is "file"
A working definition, suitable at this stage, is
"something about which an organization keeps
data"
An entity may be physical, e.g. Person,
Building, Machine etc, or conceptual, e.g. Cost
centre, project, etc.
40.
41.
42. ENTITY LIFE HISTORY
Entity Life Histories (Elhs) look at a system
from a third viewpoint, providing a means of
representing how entities change within a
system with the passage of time
Elhs start with the creation of an entity,
record the sequence of changes which take place
during its life within the system and end with its
removal from the system
43. ELHS & PROCESSES
Elhs are used to help define :
the logic associated with update processes
an examination of processes provides a
starting point to describe ELH concepts and
terminology
ELHS are concerned with update processes
only
44. Facilitate more focus on reducing maintenances
and time effort in system development
Integrate change when needed
Widely useful in industry - proven techniques
Part of career growth in IT - lots of interesting
and well-paying jobs!
Shows a steep increase in demand for systems
analysis skills
CONCLUSION