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Video Title: Data Flow Diagram
Description: Data Flow Diagram
Watch more Videos at https://www.tutorialspoint.com/videotutorials/index.htm
Lecture By: Mr. Arnab Chakraborty, Tutorials Point India Private Limited
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We are going to discuss
a data flow diagram,

in short, we will
usually call it as a DFT.

So, in case of a data flow diagram we want
to show that how it is flowing.

But in case flowchart, where we usually
show how the control is flowing.

So, that is the basic difference between
the data flow diagram and the flowchart.

So, data flow diagram is as graphical
representation The definition of flow of

data in an information system.

And it is capable of
depicting inflow, that is

in data flow, out data
flow and our stored data.

The DFD does not mention anything about
how the data is flowing through the system.

So, it will depict that
what are the inflow of

data, outflow
of data and what is the data stored.

It does not indicate that how the data is
flowing.

So, this is a prominent difference between
DFD and our flowchart.

In case of a flowchart, the flowchart depicts
flow of control in our program modules.

So, how the control
is flowing through our program modules,

that will be
depicted graphically using a flowchart.

DFD depicts flow of data in the system at
various levels.

And it does not contain any control or
branch elements.

So, that is one another difference with
the flowchart.

In case of DFD, we usually start with the
level 0 DFD.

And also it is known as context level DFD.

Or sometimes we usually call it as context
diagram.

Then we shall go for level 1, level 2,
level 3.

In this way, we shall go for more
detailing about the data flow diagrams.

So, types of DFD.

So, data flow diagrams are having mainly
two types.

One is the logical DFD.

Another one is the physical DFD.

So, the type DFD concentrates on the
system process.

So, in case of logical
DFD, it concentrates on

the system process and flow of data
in the system.

For example, in a banking
software system, how

the data will move
between different entities?

Now, the question is coming in mind,
what is entity?

Entity is nothing which is having a data
source or information source.

So, from one entity to another entity,
the data will be flowing.

But in case of physical DFD, this type of
DFD shows how the data flow is actually

implemented in the system.

It is more specific and close to the
implementation of the system.

So, here we are having different DFD
components.

So, let me discuss them one by one.

So, DFD can
represent source, destination, storage and

flow of data using this following set of
components.

So, this is our entity.

So, this entity is nothing but actually
we have discussed

that one that is
a source of information or source of data.

We are having this processes.

We are having this data store and this is
our data flow.

So, entities.

So, let me discuss them one by one.

Entities.

So, entities are sources and destinations
of information data.

Entities are represented
by rectangles as you

have seen
here and with their respective names.

And these names must be very much
purposeful, not ambiguous.

From the name, we should get the idea what
is the purpose of the entity.

Next one is the process.

So, processes
are nothing but activities and actions

taken on the data are
represented by systems.

So, a circle or round-aged
rectangles can also

be used to denote
this particular process.

So, what is the process?

Process will actually
denote the activities

which are to be performed
on this set of data.

So, next one we are going to discuss that
is our data storage.

So, there are two variants of data
storage.

It can be either be represented by a
rectangle with absence of both the smaller

sides or as an open-sided rectangle with
only one side is missing.

So, here you see here only one side is
missing.

Otherwise, we can just miss this one and
also this one both.

So, there are two representations I have
shown one of them.

Next one is our data flow.

So, that means, the last component.

So, movement of data is shown by pointed
arrows and data movement is shown from the

base of the arrow as its source towards
the head of the arrow as the destination.

So, wherever we are having the arrow,
so that is the destination part and where

this arrow is missing that is the source
part of our data.

So, at first we are going to discuss the
level 0 DFD.

So, here we have discussed
already that DFDs

will
be drawn into multiple different levels.

So, highest abstraction level DFD is known
as the level 0 DFD, which depicts the

entered information system as in one diagram
and concealing the underlying details.

So, here you just consider
one level 0 DFD and here we are having

customers and here we are having
the online shopping system.

That is a full system, that is a whole
system we have denoted in this level 0 DFD.

And this level 0 DFDs are also known as
context level DFD.

And sometimes we usually call it as a
context diagram also.

So, here we are having customers.

So, customers will produce orders and that
will be coming to this online shopping

system and then delivery will be made.

So, now the thing is that this online
shopping system needs some further

explanation how the
data will flow between

its different components
and the data store.

So, that has to be mentioned.

So, this is our level 0 DFD.

So, now let us go for level 1 DFD.

So, in case of level 1 DFD, here you see
the customer is still there, customers and

here this online shopping, this particular
system has got elaborated into details.

I think you are getting me.

This is our customers and this is our
online shopping system.

So, now see this is our customer and this
online shopping system has got elaborated.

So, this is known as our level 1 DFD.

So, the level 0 DFD
is Is broken down into more

specific and level 1
DPD will be originated.

So, level 1 DPD depicts
basic modules in the

system and flow of
data among those modules.

And level 1 DPD also mentions basic
processes and sources of information.

So, here we are having this order
processing.

So, that is one process, that is one activity
which will be working on our data set.

And this is our accounts, this is one
entity, this is another entity,

that is a source of data.

And this is our data store.

So, here we are having this data flow.

So, in this way this particular level 1
DPD has been drawn.

We can also go for its further details.

So, here we are having the level 2 DPDs.

So, at this level DPD shows how data flows
inside the module mentioned in our level 1.

So, in this way you can also go for level
3 DPD and level 4 in this way.

So, depending upon the complexity of the
system.

So, we shall decide that how far we shall
draw our DPDs accordingly.

Higher level DPDs can be transformed into
more specific lower level DPDs with deeper

level of understanding unless the desired
level of specification is achieved.

So, in this way, in this particular video,
we have discussed what is a DPD and what

are the its different
components, what are the

types of DPDs we
are having with some example.

Thanks for watching this video.

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