Tools of structured

system analysis and design

Management Information Systems

• Management: its an art of getting things done through people

• Information: processed form of data

• System:the set of elements and components which are joint together to achieve pre-determined obeje tive.

MIS is a study of people, technology, organization and relationship amongst them.

The term is commonly used to refer the study how individual group, organization to evaluate, design, implement, manage and utilize system to generate the information to improve efficiency and effectiveness of decision making.

CONTINUED….

HISTORY

1980: Central Computer and Telecommunications Agency (CCTA) evaluate analysis and design methods.

1983: SSADM made mandatory for all new information system developments

1984: Version 2 of SSADM released

1986: Version 3 of SSADM released.

1990: Version 4 launched

1995: SSADM V4+ announced, V4.3 launched

Structured Systems Analysis and Design

Structured Systems Analysis and Design Structured Systems Analysis and Design (SSAD) is a systems approach to Method is a systems approach to the analysis and design of information the analysis and design of information systems.

Benefits Of SSAD

• Improve productivity• Improve flexibility• Improve quality by reducing error rates• Deliver the system to users on time • Avoid IT developers’ bureaucracy• Deliver systems that meets user's needs

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.

• Software developers: Illustrate and interpret software application relationships, actions, and connections.

• Program managers: Show high-level static software structures in presentations and specification documentation.

The uses of SSAD software by different people

Tools of SSAD

Data Flow DiagramData DictionaryDecision TreeStructured EnglishDecision Table

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.

Contains 4 graphic symbols

• Source/destination• Data flow• Process• Data store

Source/destination• Sign: Square.

• Symbol:

• Meaning: source/destination

• Description: It represents source/destination of system data.

Data Flow

• Sign: Arrow

• Symbol:

• Meaning: Data Flow

• Description:It identifies the data flow; it is a pipeline through which the data flows.

Process• Sign: circle/ bubble

• Symbol:

• Meaning: Process

• Description: It represents a process that transforms incoming data flow into outgoing flow.

Data store

• Sign: Rectangle

• Symbol:

• Meaning: Data store

• Description:It represents data store.

Rules for constructing /drawing DFD

• Processes should be named and numbered.• The direction of flow is from top to bottom

from left to right.• The name of the data stored, sources and

destination 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.

In case of payroll system to prepare salary statement for each employee. Data flow for such system can be represented as-

Employee Data Employee

Accounts Dept Employee file

Payroll processing

Salary statement

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 s supports documentation in a better way.• It serve as common database for programmer

and can be also used for control purposes.

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. Data structure contains data elements as its field

3.Data flows :

Data flow are nothing but data structures in motion, whereas data stored are data structures at rest.

Rules for constructing Data Dictionary

1.The terms used to describe data structures are always in capital letters.

2. Multiple word names are hyphenated.

3. Assigned names should be straightforward and user oriented.

4. There should be names for every data flow, data store, data structure and data element.

5. Consistency checks should be performed.

6. Identification numbers of the process and their names should be mentioned in the data dictionary.

7. Aliases must be discouraged.

STRUCTURED ENGLISH

Structured English is the use of the English language with the syntax of structured programming. Thus structured English aims at getting the benefits of both the programming logic and natural language.

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.

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

ENDIF

ENDIF

ELSE

Reject

ENDIF

DECISION TREE

• The logic of the process, which may not be very clear through DD, can easily be represented using a graphic representation, which looks like the branches of a tree, called decision tree.

• A decision tree has a many branches as there are logical alternatives. It is easy to construct, read and update.

DECISION TABLE

• Decision table is 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,etc.