Data Flow Diagram Example for an Online Banking System

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Level 0: Context Diagram

• Description: The Context Diagram provides an overview of the entire system and shows the interaction between the system and external entities.
• External Entities:
  1. Customer: Interacts with the system to manage their bank account, perform transactions, and view account details.
  2. Bank Database: Stores account information, transaction history, and user authentication data.
• Data Flows:
  1. Customer sends a request for login, account information, or transactions.
  2. The system processes these requests and retrieves or updates information in the Bank Database.
  3. The system sends responses back to the Customer, such as account balance, transaction status, or login confirmation.

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Level 1: Decomposition Diagram

• Description: The Level 1 DFD breaks down the major processes of the system.
• Processes:
  1. 1.0 User Authentication
     • Inputs: Login credentials (username and password) from the Customer.
     • Outputs: Authentication result (success or failure).
     • Data Store: Bank Database for verifying credentials.
  2. 2.0 View Account Information
     • Inputs: Request for account details from the Customer.
     • Outputs: Account balance, account number, and account details.
     • Data Store: Bank Database to retrieve account information.
  3. 3.0 Perform Transactions
     • Inputs: Transaction request (e.g., money transfer, bill payment) from the Customer.
     • Outputs: Transaction confirmation or error message.
     • Data Store: Bank Database to update account balances and transaction history.
  4. 4.0 View Transaction History
     • Inputs: Request for transaction history from the Customer.
     • Outputs: List of past transactions.
     • Data Store: Bank Database to retrieve transaction history.

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Level 2: Detailed Processes

Here’s a detailed breakdown of the “Perform Transactions” process.

• Process: 3.0 Perform Transactions
  • 3.1 Validate Transaction Details
    • Inputs: Transaction details from the Customer (e.g., account number, amount).
    • Outputs: Validated transaction or error message.
    • Data Store: Bank Database to check account status and balance.
  • 3.2 Execute Transaction
    • Inputs: Validated transaction details.
    • Outputs: Updated account balances.
    • Data Store: Bank Database to perform the transaction and update balances.
  • 3.3 Generate Transaction Confirmation
    • Inputs: Transaction execution result.
    • Outputs: Confirmation message to the Customer.

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Data Flows Description

1. From Customer to System: Login credentials, account information requests, and transaction requests.
2. From System to Customer: Login results, account details, transaction confirmations, and transaction history.
3. From System to Bank Database: Queries for authentication, account details, and transaction updates.
4. From Bank Database to System: Retrieved data for account details and transaction history.

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Diagram Layout (Description)

1. Customer: Positioned on the left side of the diagram, with arrows pointing to and from the processes in the system.
2. Processes (1.0, 2.0, 3.0, 4.0): Placed in the center, with data flows connecting to the Bank Database and the Customer.
3. Bank Database: Positioned on the right side, connected to each process with bidirectional data flows.