What is DFD? How to design DFD, Symbols, examples full explanation

Summary

The 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

• 📊 **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.
• 🔍 **Why Use DFD?**: It helps in visualizing the system's processes and data flow, aiding in understanding and analyzing both existing and proposed systems.
• 📱 **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.
• 👤 **Entities (External Entities)**: DFD includes entities that interact with the system, such as users, which are shown as sources or sinks of data.
• 🔄 **Data Flow**: Data movement within the system is depicted using arrows, indicating the direction and path of data transfer.
• ⭕ **Processes**: Circular shapes represent processes, which are the actions performed on data, like issuing or returning a book in a library system.
• 💾 **Data Stores/Databases**: Parallel lines symbolize data stores or databases, where data is stored, read from, or written to.
• 🚫 **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.
• 🌟 **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.
• 📝 **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

00:00

📊 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.

05:01

🔍 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.

Keywords

💡Data Flow Diagram (DFD)

A Data Flow Diagram (DFD) is a graphical representation of the 'flow' of data through an information system, modeling its process aspects. In the video, DFD is central to illustrating how data moves from one process to another within an application, such as from a login page to a home page. The script uses the DFD to explain the movement and transformation of data within software systems, emphasizing its importance in system design and analysis.

💡Entity

In the context of the video, an 'entity' refers to an external element that interacts with the system, such as a user. It is depicted as a source or sink in a DFD, representing where data enters or exits the system. The script mentions entities like users of the 'Gate Smashers' app, highlighting how they interact with the system by providing data inputs and receiving outputs.

💡Data Flow

Data flow is the movement of data within a system, from one process to another or between processes and data stores. The video uses the term to describe how information travels through an application, such as when a user logs in and the system processes the login data to direct the user to the home page. The script emphasizes the importance of understanding data flow for system analysis and design.

💡Process

A 'process' in the video refers to the functions or operations performed on data within the system. It is represented by a circle in a DFD and signifies the transformation or manipulation of data. For instance, the script describes the process of logging in as a transformation of user credentials into a session on the app's home page.

💡Data Store

A 'data store' or 'database' in the video is where data is persistently stored for later use. It is depicted by parallel lines in a DFD. The script explains that applications use databases to store and retrieve data, such as user information or content, and that these interactions are crucial for the system's functionality.

💡Control Flow

While not explicitly mentioned, 'control flow' is implied in the video's discussion of how the system directs data movement and process execution. It refers to the sequence in which processes are executed, which is often determined by the data flow. The script uses the example of navigating through an app to show how control flow is managed behind the scenes as users interact with the system.

💡Graphical Representation

The video emphasizes the use of graphical representations, such as DFDs, to visualize and communicate the structure and flow of data within a system. It is a key tool for designers and analysts to understand and explain how a system operates. The script describes how DFDs help in mapping out the flow of data from user interactions to backend processes.

💡System Analysis

System analysis is the process of evaluating and understanding a system to inform its design or improvement. The video uses DFDs as a tool for system analysis, allowing for the examination of existing or proposed systems. The script illustrates how DFDs can be used to predict the sequence of pages and data flows in an application before it is implemented.

💡User Interaction

User interaction is a key aspect of the video's discussion, focusing on how users engage with an application and how this interaction is managed by the system. The script uses examples like logging into an app to show how user actions trigger data flows and process executions within the system.

💡Competitive Examination

The video script mentions 'competitive examination' as a context for the importance of understanding DFDs and related concepts. It suggests that the knowledge of DFDs and data flow is not just academic but also practical for competitive exams where such concepts are tested. The script advises focusing on key points rather than getting lost in theory.

💡Rules of Data Flow

The 'rules of data flow' are principles that govern how data can move within a system, as outlined in the video. These rules define valid paths of data movement, such as from an entity to a process or between processes, and highlight invalid paths, like direct communication between entities without a process. The script uses these rules to explain the correct way to represent data flows in a DFD.

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.