08. Ankita

14. Ashutosh

18. Samiksha

19. Laksh

A data flow diagram (i.e. DFD) is a graphical system model that shows all of the main requirements for an information system in one diagram: inputs and outputs , processes and data storage.

Process

Data Flow

Data store

External Agent

Real Time Link

Processes should be named and numbered for easy references.

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

When a process is exploded into lower level details they are numbered PHYSICAL and LOGICAL DFDs.

Readable

Internally Consistent

Accurately represents system requirements.

Minimizing complexity

1. 7+-2 (Miller’s number)

2. Interface minimization

Data flow consistency

A data dictionary is a structured repository of data about data.

The three classes of items to be defined in data dictionary are as follows:

Data Element:

The smallest unit of data that provides for no further decomposition.

Data Structure:

A group of data elements handled as a unit.

Data Flow & Data Store:

Data flows are data structures in motion, whereas data stores are data structures at rest.

An event is some change or activity that takes place in the user’s

environment that stimulates a response from the software

system

An event-response table (also called an event table or an event

list) lists all such events and the behavior the system is expected

to exhibit in reaction to each event.

# Event Table #

Event: An event which causes the system to do something.

Trigger: A signal that tells the system that an event has occurred,

either the arrival of data needing processing or a point in time.

Source: the source of an event (an actor for an EE and the system for

a TIE and CIE).

Activity: Behaviour that the system performs when an event occurs.

Response:An output, produced by the system, that goes to a

destination

Destination: An actor that receive the result of an

event execution

Event Trigger Source Activity Response Destination

In the event table, there are three types of events, that is:

1. External Event (EE): an event that occurs outside of the system,

usually initiated by external actor or user;

For example:

Student wants to search for a book item.

2. Temporal Internal Event (TIE): an event that happens when the system

reaches a specific point of time;

For example:

time to print book items report.

3. Conditional Internal Event (CIE): an event occurs when something

happens inside the system and the system must initiate some process

to response for this event;

For example:

student reordered new books when the reordered point is reached.

Example (student wants to search for a book item) and for an EE, we can split this event into three main parts:

Student- Source

EE Search- Action

Book item-affected object

The TIE example (time to print book items report) can be divided into three main parts as the following:

Time or "System"- Source

TIE Print- Action

Book item- Affected object

Finally, we can split the CIE (student reordered new books when the reordered point is reached) into the following three main parts:

Student - Source

CIE Reordered- Action "if the reordered point is reached"

Book item- Affected object

Event Trigger Source Activity Response Destination

Customer

contacts

Owner

Contact

request Customer

Personal/Tele

-Contact

Meet/Receive

Call

Owner

Customer

booked

Vehicle

Rent a

Vehicle

request

Customer Personal/Tele

-Contact

Vehicle

approved

Owner

Owner

contact’s

Driver

Work

request

Owner Personal/Tele

-Contact

Drive/will not

Drive.

Driver

Owner

contacts

Agent

Contact

request

Owner Tele-Contact Request fulfilled Agent

Owner ask

for

Payment

Payment

request

Owner Payment by

Cash/Cheque

Full/Partial

Payment Done

Customer

Driver ask

contact

Details

Details

request

Driver Personal/Tele

-Contact

Give Contact

Details

Customer

Driver ask

payment

Payment

request

Driver Payment by

Cash/Cheque

Full payment

Done

Owner

-: Event Table of a Travels Business :-

Event table defining functional requirements to Traditional Approach model, Data Flow Diagrams

The DFD integrates the Event table and the ERD

When event gets triggered(input) the data flow into system has to respond(output)

External gents, data flow, & the process come from DFD about the event is place in event table

An event table is used to create a data flow

diagram by analyzing each event and the

data used and produced by the event

Every row in an event table represents a data

flow diagram fragment and is used to create

a single process on a data flow diagram