Tools of Structured Analysis

8/2/2019 Tools of Structured Analysis

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Prestige Institute

of

Management & Research, Indore

Tools Of Structured Analysis

Submitted To:

Prof. Bhavna Sharma

Submitted By:

Ankit Kumar Gupta

Rakesh Goliya

Sanjay Chouhan

Ish KumarMBA(FT) 2nd Sem. Sec. B


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In this session

Structured Analysis

Data Flow Diagram

Data Dictionary

Decision Trees

Decision Tables

InputProcess - Output

Hierarchy plus InputProcess - Output

Information System Planning Process


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Structured Analysis

The Word STRUCTURED In Structured Analysis Means:

The method attempt to structure the requirements determination process ,beginning with documentation of the existing system.

The process is organized in such a way that it attempts to include all relevant details

that describe the current system.

It is easy to verify when relevant details that describe the current system.

The identification of requirements will be similar among individual analysts and will

include the best solutions and strategies for systems development opportunities.

The working papers produced to document the existing and proposed systems are

effective communication devices.


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Meaning Of Structured Analysis

Structured analysis is a set of techniques and graphical tools that allow the

analyst to develop a new kind of system specification that are easily

understandable to the user.

Structured analysis is a development method for the analysis of existing

manual or automated systems, leading to the development of specifications

for a new or modified system. When systems analysts approach an unfamiliar

situation, there is always a question of where to begin the analysis. Structured

analysis allows the analysts to learn about a system or process(activity) in a

manageable and logical way while providing a basis for ensuring that pertinent

details do not get overlooked.


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Characteristics Of Structured

Analysis

Graphical with supporting text.

Allow system to be viewed in a top-down and

partitioned fashion.

Minimum redundancies.

Reader should be able to predict system

behavior.

Easy to understand by user.


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Components Of Structured

Analysis

Graphic Symbols:Icons and conventions for identifying and describing the components of a

system and the relationships among these components.

Data Dictionary:Descriptions of all data used in the system. Can be manual or automated (may

be included in a larger project dictionary that also contains descriptions

of processes making up the system.

Procedure and Process Description:

Formal statements using techniques and language that enable analysts todescribe important activities that make up the system.

Rules:Standards for describing and documenting the system correctly and

completely.


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Goals Of Structured Analysis

Improve Quality and reduce the risk of system

failure.

Establish concrete requirements specifications

and complete requirements documentation.

Focus on Reliability, Flexibility, and

Maintainability of system.


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Tools Of Structured Analysis

Data Flow Diagram

Data Dictionary

Decision Trees

Decision Tables

InputProcess - Output

Hierarchy plus InputProcess - Output


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Data Flow Diagrams

A graphic tool used to describe and analyze the movement of data through a

system - manual or automated including the process, stores, of data and delays

in the system.

A Data Flow Diagram (DFD) is a graphical representation normally designed by asystem analyst and is used as a reference point by the programmer which

portrays the "flow" of data through an information system. It is primarily used

for the visualization of data processing for the structured design of an

information system. It is common practice for a database designer to begin the

process by drawing a context-level DFD, which shows the interaction between

the system and outside entities.

A Data Flow Diagrams also known as a Bubble Chart, has the purpose of

clarifying system requirements and identifying major transformations that will

become programs in system design. A DFD consists of a series of bubbles joined

by lines. The bubbles represent data transformations and the lines represent

data flows in the system.


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Types Of Data Flow Diagrams

Physical Data Flow Diagrams

An implementation-dependent view of the current system, showing what

tasks are carried out and how they are performed.

Physical characteristics include:Name of the people.

Form and document names or numbers.

Names of Departments.

Logical Data Flow Diagrams

An implementations-independent view of a system, focusing on the flow of

data between processes without regard for the specific device, storage

locations or people in the system.

Example : computer , file cabinets etc.


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Data Flow Diagrams Symbols

Square defines a source or destination of data.

Arrow identifies data flow, means the data in motion. It

is a pipeline through which information flows.


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Continued

Circle or a bubble represents a process that transforms

incoming data flow into outgoing data.

Open rectangle is a data store, or data at

rest, or a temporary repository of data


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Constructing a Data Flow

Diagram

Processes should be named and numbered for easy reference.

The direction of flow is from top to bottom and from left to right .

Data flow from the source to destination, although they may flow back to a source.

When a process is exploded into lower level details, they are numbered.

The names of data stores, sources, and destinations are written in

capital letters. Process and data flow names have the first letter of eachword capitalized.


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Advantage & Disadvantages Of

DFD

Advantages:

Represents data flows.

May be used at high or low level of analysis.

Provides good system documentation.

Process bubbles can be hierarchically decomposed into sub-DFDs;

the inputs and outputs must match at all levels of decomposition, so

the design has validation.

Disadvantages:

Weak in its display of input and output details.


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Example Of Data Flow Diagram

General Model Of Publishers Present Ordering System


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DataDictionary

A Data Dictionary is a catalog - a repository of the elements in a system.

Although we give descriptive names to the data flows, process and data stores in a

DFD, it does not give the details. Hence to keep the details of the contents of data

flows, process and data stores we also require a Data Dictionary.

The three classes to be defined are:

Data Elements: Smallest unit of data that provides for no further decomposition.For example: date consists of day, month and year.

Data Structure: A group of data elements handled as a unit.For example: phone is a data structure consisting of four data

elements: Area-Code-Exchange-Number-Extension.

Data Flows and Data Stores: Data flows are data structures in motion, whereas

data stores are data structures at rest. A data store is a locationwhere data structure are temporarily located.


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Continued

Data Dictionary

Data Elements

Data Structures

Data Flow Data Store

Smallest Unit of

Data

Group of Data

Elements

Groups of Data

Structures


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Advantages Of DataDictionar

Managing Detail:Large systems have huge volumes of data flowing through them in

the form of documents, reports and even conversations. Similarly , many

different activities take place that use existing data or create new details.

Quite frankly , it is impossible for system analysts to remember it all. So , weuse data dictionaries to store huge volume of data into the best organized

and most effective way.

Communicate Meaning:

Data Dictionaries assist in ensuring common meanings for systemelements and activities. Data dictionaries record additional details about the

data flow in a system so that all persons involved can quickly look up the

description of data flows, data stores or processes.


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Continued

Document System Features:Documenting the features of an information system is the third

reasons for using data dictionaries. Features include the parts or components

and the characteristics that distinguish each.

Facilitate Analysis:

The fourth reason for using data dictionaries is to determine

whether new features are needed in a system or whether changes of any

type are in order.

Locate Errors and Omissions:

Having system in a dictionary about these system characteristics

transactions , inquiries , data and capacity will tell you a great deal about a

system and allow you to evaluate it.


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Decision Trees

A Decision tree is a diagram that presents conditions and

actions sequentially and thus shows which conditions to

consider first, which second and so on. It is also a method of

showing the relationship of each condition and its permissible

actions.

A structure that can be used to divide up a large collection

of records into successively smaller sets of records by applying

a sequence of simple decision rules.

A decision tree model consists of a set of rules for dividing a

large heterogeneous population into smaller, more

homogeneous groups with respect to a particular target

variable.


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Advantages Of Decision Tree

Easy to understand.

Map nicely to a set of business rules.

Applied to real problems.

Make no prior assumptions about the data.

Able to process both numerical and categorical data.


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Disadvantages Of Decision Tree

Output attribute must be categorical.

Limited to one output attribute.

Decision tree algorithms are unstable.

Trees created from numeric datasets can be

complex.


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Example Of Decision Tree

Bookstores get a trade discount of 25%; for

orders from libraries and individuals, 5%

allowed on orders of 6-19 copies per booktitle; 10% on orders for 20-49 copies per

book title; 15% on orders for 50 copies ormore per book title.


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Type Of Customer DiscountSize Of Order

Discount

Policy

Bookstore

Libraries or

Individuals

6 or More

Less than 6

50 or More

20 - 49

6 - 19

Less than 6

25%

NIL

15%

10%

5%

NIL

Continued


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Decision Tables

A decision table is a table of contingencies for defining a problem and

actions to be taken. It is a single representation of the relationships

between conditions and actions.

Decision Tables are a graphic method for describing the logic of

decisions. The decision table lists a set of conditions plus a set ofactions and identifies different combinations of decision which lead to

different combinations of actions. These Different combinations are

termed rules. A decision table is simply a table showing the various

actions to be taken for different combinations of conditions.

Decision tables are a precise yet compact way to model complicated

logic. Decision tables, like if-then-else and switch-case statements,

associate conditions with actions to perform.


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Decision Tables Characteristics

The decision table is made up of four sections :

Conditions Statements:

The condition statements identifies the relevant condition.

Conditions Entries:Condition entries tell , which value , if any , applies for a particular

situation.

Action Statements:

Action Statements list the set of all steps that can be taken when acertain conditions occurs.

Action Entries:

Action Entries show what specific actions in the set to take when

selected conditions or combinations of conditions are true.


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Steps To Create a Decision Table

Determine the most relevant factors to be considered in

making a decision.

Determine the most feasible steps or activities under

varying conditions. This identifies the actions.

Study the combinations of conditions that are possible.

Fill the table with decision rules.

Mark action entries with X to signal actions to take ,

leave cell blank or mark with a dash to show that no action

applies to that row.

Examine the table for redundant rules or for

contradictions within rules.


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Advantages Of Decision Table

Decision tables are normally used in place of flowcharts because of the

following reason:

They provide concise descriptions of logically complex situations.

They are easier to draw and change than flowcharts.

They provide more compact documentation. A small table can replace

several pages of flowcharts.

It is also easier to follow a particular path down one column than throughseveral flowcharts pages.


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Disadvantages Of Decision Table

Large decision tables can become incomprehensible and difficult to

modify.

Flowcharts are better able to express the total sequence of events

needed to solve a problem.

Flowcharts are more familiar to, and are preferred by, many

programmers and beginners.


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Input Process Output Chart

The IPO diagram is a visual representation of a process or activity. It

lists input variables and output characteristics.

It is useful in defining a process and recognizing the input variables

and responses or outputs.

Input Process Output is what you put in, what you use both input and

output for, and also what you get out.

For example you might put in your monthly expenditure and income

(input) , then you can work out your average (process) and then

finally create a graph (output).


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Continued
http://4.bp.blogspot.com/_Mhgbe8G_OpU/TBWZzCKwOVI/AAAAAAAAAns/5mQNdBfrAuc/s1600/isblueprint1.jpg


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Hierarchy Plus Input Process

Output Chart

HIPO is a forms-driven technique in that standard forms are used to

document the information. It consists of a hierarchy chart and an

associated set of input/process/output charts.

HIPO captures the essence of top down decomposition; it describes

the data input and output from processes and define the data flow

composition.

A HIPO model consists of a hierarchy chart that graphically represents

the programs control structure and a set of IPO (Input-Process-

Output) charts that describe the inputs to, the outputs from, and the

functions (or processes) performed by each module on the hierarchy

chart.


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Steps To Create a HIPO Chart

Begin at the highest level of abstraction and define the inputs to the

system and the outputs from it in aggregate terms.

Identify the processing steps by those that convert input into

output.

Document each element using HIPO diagram notation and the

associated treelike structure.

Identify sub processes and their respective inputs and outputs.

Continue decomposition until the processes cannot be decomposed

any further.


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An overview diagram for the payroll processing module,''Calculate Each Employee's Pay,'' is shown in the Figure below.

Example..


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ThankYou


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Documents

Tools of Structured Analysis