What is DFD? How to design DFD, Symbols, examples full explanation
Summary
TLDRThe video script explains the concept of a Data Flow Diagram (DFD), a graphical representation of data movement within a system. It highlights the importance of DFDs in analyzing both existing and proposed systems, illustrating how data flows from one module to another. Key elements such as external entities, data flows, processes, and data stores are discussed, with emphasis on their roles in the system. The script also outlines the rules governing data flow, emphasizing that direct communication between entities or data stores without a process is invalid. This overview is crucial for understanding system design and data management in applications like mobile apps and databases.
Takeaways
- π **Data Flow Diagram (DFD) Purpose**: DFD is a graphical tool used to represent the 'flow' of data through an information system, modeling the system's process and data movement.
- π **Why Use DFD?**: It helps in visualizing the system's processes and data flow, aiding in understanding and analyzing both existing and proposed systems.
- π± **Application Example**: The script uses the example of a mobile app, like 'Gate Smashers', to explain how DFD can represent the navigation between different pages and modules.
- π€ **Entities (External Entities)**: DFD includes entities that interact with the system, such as users, which are shown as sources or sinks of data.
- π **Data Flow**: Data movement within the system is depicted using arrows, indicating the direction and path of data transfer.
- β **Processes**: Circular shapes represent processes, which are the actions performed on data, like issuing or returning a book in a library system.
- πΎ **Data Stores/Databases**: Parallel lines symbolize data stores or databases, where data is stored, read from, or written to.
- π« **Rules of Data Flow**: The script emphasizes that data can flow between entities and processes, processes and data stores, but not directly between entities or stores without involving processes.
- π **Key Elements**: The four main elements of DFD are external entities, data flow, processes, and data stores, with the script highlighting their importance in system analysis.
- π **Practical Focus**: The script advises focusing on practical understanding over deep theory, especially for competitive exams where application of concepts is more important than theoretical knowledge.
Q & A
What is the primary purpose of a Data Flow Diagram (DFD)?
-The primary purpose of a Data Flow Diagram (DFD) is to graphically represent the flow of data within an information system, illustrating the movement of data from one module to another and how it is processed.
Why are Data Flow Diagrams important in software development?
-Data Flow Diagrams are important in software development because they help in visualizing the system's data flow, which aids in understanding the system's structure and functionality, facilitating communication among stakeholders, and analyzing both existing and proposed systems.
Can you explain the concept of 'entity' in the context of DFD?
-In DFD, an 'entity' or 'external entity' refers to a source or sink that interacts with the system by providing input (source) or receiving output (sink). It can be a user, a department, or any external system that exchanges data with the system being modeled.
What does the term 'data flow' represent in a DFD?
-In a Data Flow Diagram, 'data flow' represents the movement of data between different components of the system. It is depicted as arrows that show the direction and path of data as it is processed and transferred within the system.
How are processes depicted in a DFD, and what do they signify?
-Processes in a DFD are typically represented by circles. They signify the work being done within the system, such as data transformation or manipulation, and are the actions that change the state or data within the system.
What is the role of a 'data store' in a DFD?
-A 'data store' in a DFD, often represented by parallel lines, signifies a place where data is stored, such as a database or a file. It indicates where data is kept, retrieved, updated, or deleted within the system.
What are the four main elements of a DFD?
-The four main elements of a Data Flow Diagram are: 1) External Entities (sources or sinks), 2) Data Flows (represented by arrows), 3) Processes (represented by circles), and 4) Data Stores (represented by parallel lines).
What is the significance of the term 'bubble chart' in relation to DFDs?
-The term 'bubble chart' is another name for a Data Flow Diagram, emphasizing its graphical nature where the 'bubbles' represent different processes or components within the system, and the connections between them show the flow of data.
Why are rules of data flow important in DFD?
-Rules of data flow are important in DFD because they dictate the valid pathways for data movement within the system. These rules ensure that the diagram accurately reflects the system's operations and helps in identifying any potential issues or inefficiencies in data handling.
Can data flow directly between external entities without involving a process in a DFD?
-No, in a DFD, data cannot flow directly between external entities without involving a process. Data must pass through a process, which acts as an intermediary, ensuring that the flow of data is controlled and documented.
How does a DFD help in the analysis of an existing or proposed system?
-A DFD helps in the analysis of an existing or proposed system by providing a clear visual representation of how data moves through the system. It allows analysts to identify the sequence of data processing, potential bottlenecks, and areas for improvement, which is crucial for system design and optimization.
Outlines
π Introduction to Data Flow Diagrams (DFDs)
This paragraph introduces the concept of Data Flow Diagrams (DFDs), explaining their purpose and why they are essential in software development. DFDs are graphical representations of the 'flow' of data through an application or system, illustrating the movement from one module to another. The example of a mobile app, 'Gate Smashers,' is used to explain how data moves from the login page to the home page and then to specific content pages. The paragraph emphasizes that DFDs are not just about the physical movement but about the control and data flow at the backend. DFDs are also known as Bubble charts and are crucial for communicating with users, managers, and other stakeholders. They are used to analyze both existing and proposed systems, helping to understand the sequence of data processing and transfer. The importance of not getting too caught up in theory but focusing on practical application, especially for competitive purposes, is highlighted.
π Key Elements and Rules of Data Flow Diagrams
This paragraph delves into the main elements of a Data Flow Diagram: external entities, data flows, processes, and data stores. External entities, or sources/sinks, are those that provide or receive data to/from the system. Data flows are represented by arrows, indicating the direction of data movement. Processes are depicted as circles and represent the work being done, such as issuing or returning a book. Data stores, analogous to databases, are shown with parallel lines and involve read and write operations. The paragraph outlines the rules of data flow, such as the valid movement of data between entities and processes, and between processes and data stores. It also clarifies that direct communication between external entities or between data stores without involving processes is not allowed. The importance of understanding these rules for practical application and potential examination questions is emphasized.
Mindmap
Keywords
π‘Data Flow Diagram (DFD)
π‘Entity
π‘Data Flow
π‘Process
π‘Data Store
π‘Control Flow
π‘Graphical Representation
π‘System Analysis
π‘User Interaction
π‘Competitive Examination
π‘Rules of Data Flow
Highlights
Data Flow Diagram (DFD) is used to represent the flow of data within a system.
DFD is essential for understanding the movement of data between different modules of an application.
DFD helps in visualizing the process flow and the interaction between system components.
The example of 'Gate Smashers' mobile app is used to explain the concept of DFD.
DFD is a graphical tool that aids in communication between users, managers, and other stakeholders.
DFD can be used to analyze both existing and proposed systems for better planning and design.
DFD is also known as a Bubble chart, representing data flow graphically.
The importance of understanding data flow in applications like Zomato, Ola, and Uber is emphasized.
DFD helps in predicting the sequence of pages and data flow before implementation of an app.
The main elements of DFD include external entities, data flows, processes, and data stores.
External entities are sources or sinks that supply or receive data to/from the system.
Data flows are represented by arrows, indicating the direction of data movement.
Processes are depicted as circles and represent the work being done within the system.
Data stores or databases are shown with parallel lines, indicating data storage and retrieval.
Rules of data flow dictate valid movements between entities, processes, and data stores.
Direct communication between external entities or data stores without processes is not allowed.
The importance of focusing on practical application over theoretical knowledge for competitive purposes is stressed.
Transcripts
Data Flow Diagram,
What is its purpose?
Why are we making DFD?
What it is?
So see, any software
or application, you are using,
So, there are multiple pages in it.
This means, like, you open the app of
Gate Smashers in your mobile.
As soon as you click on the logo.
So what will open?
The first time you are opening it,
Then it will ask you for the login information
that you have to log in.
That means there is a login page.
On that login page, your username,
password, whatever they are asking for.
You filled into it.
As soon as you put it,
What will happen after that?
It will take you to the home page.
It may also be that the first time,
will ask you to register.
So you have to enter your information.
And after entering,
your registration will be completed.
Then you will use it
and go to the home page.
so what is actually happening,
that you're traveling from one page to another,
from one module to another module.
You are moving from one module to another module.
See, means you are not actually moving
What is actually moving?
Control is moving at backend
Data is moving.
Initially, your data was on the login page,
then it turned around &
came to the home page.
When we clicked on Rajasthan content,
it went to the Rajasthan content.
After that, you click on the DBMS videos
So your control goes into it.
So what is happening?
In a way, movement is happening,
data is flowing
The same things,
When we represent
all those things in a graphical way,
so it is called DFD.
The same story is written here.
A graphical tool useful for
communicating with user,
manager, and other personnel.
This means, you see,
in a way, you're users.
What are users doing?
Users are using the app of gate smashers.
Who is sitting on the backend?
Means we are trying to manage the app.
So you are interacting with us
through that app.
And what's going on there?
Data is flowing.
So the same thing we represent graphically.
So the Data flow diagram,
Take note of this too,
that the Data flow diagram is
also called a Bubble chart.
So we represent it graphically.
Useful for analyzing existing as well as
the proposed system,
this means the system that is already existing
Or the system that I want to build now.
So I can analyze it,
I would know in advance that
this page should come first then this.
Now see, any app is made,
you use any app, you use Zomato,
Ola, Uber, or anything.
So it's not that
all these things are made overnight.
NO, before implementation,
they must have made all the things
& seen that this page should come first,
Then the data flows like this.
Then the user clicks on it.
So, somewhere we mentioned
all these things in the DFD.
So just note down the main points.
The rest is theory.
Don't go too much in the theory
because we're doing it for competitive.
We are not doing it for college & university
That 10 marks question will come,
15 marks question will come.
And two pages have to be filled.
that is not our purpose.
I will keep telling you the important points.
So these are the same things that
why we are using it.
Graphical way representation
What data a system process means
what type of data processing the system.
How the data is being transferred
from one place to another,
all those things come here.
Yes, here comes
Four main elements.
I put a star mark on it.
Where I am marking the star,
that is the most important.
So here, first is source or sink.
We call it an entity.
As in DBMS, there is an entity object,
the same thing is here also.
Here we call it an external entity
or entity.
like there is a user,
what is it, an entity.
Like I'm using an ATM.
So what am I? In a way, I'm a user,
a customer
who is using the ATM?
So what happened,
the user becomes an external entity.
Then, data flow.
We represent it with a rectangle.
We represent the external entity
with the rectangle.
Data Flow
What does data flow mean?
How is your data flowing?
In which direction?
In which direction it is moving
from one place to another?
So this flow tells you.
That's how your data is moving.
It's a simple thing,
there's nothing difficult about it.
Processes. Generally, we represent
the process with the circle
processes mean what work you are doing?
Like you went to the library,
now by going to the library,
you are either getting the book issued.
So issuing a book is a process.
You are returning it
Return a book is a process.
So it's what are you actually doing?
And then data store.
you can call it a data store
You can call it a database as well.
if there is an application
then it will use a database.
So to use the database at the backend,
We also write data stores here.
And we represent it with parallel lines.
So obviously we will read the database
We'll write something in the database.
So all those processes are also in it.
Here, in the external entity
Source and sink, just note it down.
Source means an entity that
supplies data to the system,
which means the one who is giving input
means the data which is being given to the system,
we call it the source.
And the one who is taking data from the system,
we call it sink.
In the theory,
a question may be asked on this.
Data flow.
I have already told you.
we represent it with an arrow.
Then comes processes,
represented by the circle.
Obviously, arrows will be there as well.
And in this way,
we also mention it above & write it down.
So that we can understand
Actually what process they are doing,
Where is the data moving?
Now you will get more ideas from the example.
Data Store or Database.
In this way, we represent it with lines
And obviously what to do in the database?
Either to write something in the database,
to update, or to insert something.
& read means to read something from the database.
To read something from the database.
This is your most important point.
If the question comes,
it will come from this.
Rules of data flow. Make a note of this.
How data flows?
The external entity to the process.
What does external entity to the processes mean?
That you made any entity
Now from the entity,
your data can move towards processes.
Let's ask you, is it valid? Yes.
Obviously, data will move from entity to process.
Can data move from Process to entity?
Yes, it can do it too,
so both are valid.
Processes to the store and back.
Now, look, at the processes.
What can processes use at the backend?
It will use a database.
Can any arrows be drawn toward the database?
Yes, it can be drawn through processes.
can it come from?
Yes, It can come. Same read & write.
Processes to processes. Yes,
there is a process,
if another process came.
Can both processes communicate
data with each other?
Yes, they can too.
What can't happen?
The external entity to an
external entity means two entities.
There are two entities.
Can they share data with each other
without processes?
No, they can't, it's wrong.
The external entity to store
means there is an entity
and it is accessing the database,
An entity cannot access the database directly.
You will do it through any process.
Now whatever you are,
like accessing our database,
accessing your college university,
then through some applications,
through your university college applications.
You can't access the data directly.
If you are doing it directly,
then it is wrong.
Store to an external entity.
It's the same, entity to store
or store to an entity.
It can not be possible in both directions.
And store to store means a database.
The two databases, first is database 1
The second is database 2.
So, are they each other,
Can one store do to another store?
No, it can't do directly.
It can do through a process.
Direct communication,
this is most important.
If the question comes,
then it will come from this.
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