Software Engineering- ERD DFD Decision Tree and Table

Presentation ByNISHU RASTOGI

Assistant Professor

Invertis University, Bareilly

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Known as Data Flow diagram

A graphical representation of flow of data within anyinformation system

Preliminary step to create an overview of the system,which can later be elaborated

Used for the visualization of data processing

Illustrates how data is processed by a system interms of inputs and outputs.

Focus is on the flow of information, where datacomes from, where it goes and how it gets stored.

DFD

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Function

File/Database

Input/Output

Flow Lines

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Notations for DFD

Each process should have at least one input and an

output

Each data store should have at least one data flow inand one data flow out

Data stored in a system must go through a process

All processes in a DFD go to another process or adata store

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DFD rules and tips

Also known as Context Diagram

It only contains one process node that generalizes thefunction of the entire system in relationship toexternal entities

Basic overview of the whole system or process beinganalyzed or modeled

It should be easily understood by a wide audience,including stakeholders, business analysts, dataanalysts and developers.

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Level- 0 DFD

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Example of Level 0

Highlight the main functions carried out by thesystem, as you break down the high-level process ofthe Context Diagram into its sub-processes.

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Level-1 DFD

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Example of Level 1

It may require more text to reach the necessary level

of detail about the system’s functioning.

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Level-2 DFD

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Example of Level 2

Known as Entity Relationship Diagram

An entity relationship diagram (ERD) shows therelationships of entity sets stored in a database.

ER diagrams illustrate the logical structure of databases

ER-modeling is a data modeling technique usedin software engineering to produce a conceptualdata model of a information system.

Diagrams created using this ER-modeling technique arecalled Entity-Relationship Diagrams, or ER diagrams orERDs.

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ERD

To design database there are several important

components which are focused i.e.

Entity

Relationship

Attributes

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ERD Notations

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ERD Example

A decision tree gives a graphic view of the

processing logic involved in decision making and thecorresponding actions taken

The edges of a decision tree represent conditions

The leaf nodes represent the actions to be performeddepending on the outcome of testing the condition

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Decision Tree

Consider Library Membership Automation Software(LMS) where it should support the following threeoptions-

New member

Renewal

Cancel membership

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Example

New member option

Decision: When the 'new member' option is selected,the software asks details about the member like themember's name, address, phone number etc.

Action: If proper information is entered then amembership record for the member is created and abill is printed for the annual membership charge plusthe security deposit payable.

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Example contd..

Renewal option

Decision: If the 'renewal' option is chosen, the LMSasks for the member's name and his membershipnumber to check whether he is a valid member ornot.

Action: If the membership is valid then membershipexpiry date is updated and the annual membershipbill is printed, otherwise an error message isdisplayed.

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Example contd..

Cancel membership option

Decision: If the 'cancel membership' option isselected, then the software asks for member's nameand his membership number.

Action: The membership is cancelled, a cheque forthe balance amount due to the member is printedand finally the membership record is deleted fromthe database.

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Example contd..

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A decision table is used to represent the complex

processing logic in a tabular or a matrix form

The upper rows of the table specify the variables orconditions to be evaluated.

The lower rows of the table specify the actions to betaken when the corresponding conditions aresatisfied.

A column in a table is called a rule.

A rule implies that if a condition is true, then thecorresponding action is to be executed.

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Decision Table

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Decision Table of LMS

Make DFD, ERD and DT for

Hotel Management System

Inventory Management System

Hospital Management System

Railway Reservation System

Automatic Teller Machine System

College ERP System

Flipkart etc.

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Exercise