Structured Analysis and its various Tools

                                                     Structured Analysis

What is Structured Analysis?
Structured Analysis is a development method that allows the analyst to understand the system and its activities in a logical way.

It is a systematic approach, which uses graphical tools that analyze and refine the objectives of an existing system and develop a new system specification which can be easily understandable by user.

It has following attributes −

->It is graphic which specifies the presentation of application.

->It divides the processes so that it gives a clear picture of system flow.

->It is logical rather than physical i.e., the elements of system do not depend on vendor or hardware.

->It is an approach that works from high-level overviews to lower-level details.


Structured Analysis Tools
During Structured Analysis, various tools and techniques are used for system development. They are

1.) Data Flow Diagrams
2.) Data Dictionary
3.) Decision Trees
4.) Decision Tables
5.) Structured English
6.) Pseudocode

Data Flow Diagrams (DFD) or Bubble Chart

It is a technique developed by Larry Constantine to express the requirements of system in a graphical form.

->It shows the flow of data between various functions of system and specifies how the current system is implemented.

->It is an initial stage of design phase that functionally divides the requirement specifications down to the lowest level of detail.

->Its graphical nature makes it a good communication tool between user and analyst or analyst and system designer.

->It gives an overview of what data a system processes, what transformations are performed, what data are stored, what results are produced and where they flow.

Basic Elements of DFD

DFD is easy to understand and quite effective when the required design is not clear and the user wants a notational language for communication. However, it requires a large number of iterations for obtaining the most accurate and complete solution.

The following table shows the symbols used in designing a DFD and their significance:-

Symbol Name Symbol Meaning

Square          Source or Destination of Data

Arrow          Data flow

Circle          Process transforming data flow

Open Rectangle Data Store

Types of DFD

DFDs are of two types:  Physical DFD and Logical DFD. The following table lists the points that differentiate a physical DFD from a logical DFD.

1.) Physical DFD

->It is implementation dependent. It shows which functions are performed.

->It provides low level details of hardware, software, files, and people.

->It depicts how the current system operates and how a system will be implemented.

2.) Logical DFD

->It is implementation independent. It focuses only on the flow of data between processes.

->It explains events of systems and data required by each system.

->It shows how business operates; not how the system can be implemented.

Context Diagram

A context diagram helps in understanding the entire system by one DFD which gives the overview of a system. It starts with mentioning major processes with little details and then goes onto giving more details of the processes with the top-down approach.

The context diagram of mess management is shown below:

Data Dictionary

A data dictionary is a structured repository of data elements in the system. It stores the descriptions of all DFD data elements that is, details and definitions of data flows, data stores, data stored in data stores, and the processes.

A data dictionary improves the communication between the analyst and the user. It plays an important role in building a database. Most DBMSs have a data dictionary as a standard feature. For example, refer the following table:-

Sr no.	Data name	Description	No. of characters
1	ISBN	Isbn number	10
2	Title	title	60
3	Sub	Book subjects	80
4	ANAME	Author name	15

To read the next tools of structured Analysis:-
Decision Trees and Decision Tables

Structured English and Pseudocode