Returning a book to library – Data Flow Diagram – Example

Returning a book to library – Data Flow Diagram – Example

After issuing a book from library, it is arbitrary to return the book in time. In this example we will discuss about the model of returning a book to library.


This system need to accept student information as input. Student information may contain student name, student id, and registration number and so on. The best can be student ID number that is usually not repeated (although registration number is not repeated, for now I choose student Id number). Yes, not only student information is sufficient input for this system, system should also accept the name to the book to be submitted/ returned. Advantage of preparing this DFD can be; proper knowledge of Data flow, effects of external entities in the system, determination of process in the overall system.

This Data Flow Diagram was taken directly from my notes so if you have any problems in understanding it, you are kindly requested to leave comment below.

In this context diagram of DFD; general symbols of DFD are used to prepare a simple model. Students, Librarian and Head of Library are the external entities. Process name is Returning Books to Library.

Returning a book to library; Context Diagram

Returning a book to library; Context Diagram

Figure: Returning a book to Library; Context Diagram

The standard of naming process-name is; process name should be action verb that specifies the operation(see on: How do we begin to construct Data Flow Diagrams? ). Data Flow contains the data to be exchanged throughout the system from external entities to data stores through process. And obviously, entities are real objects that take part in the system.

Similarly, in Level 1 DFD external entities are same but processes are break down into two or more process; so as to clarify each of the operation separately. The process is broken into two processes; Check Book on Library and Generate Report.

Returning a book to library; Level 1 DFD

Returning a book to library; Level 1 DFD


Figure: Returning a Book to Library; Level 1 DFD

In Level 1 DFD we show the database objects used. Here we use two database; book_db and issue_db. Book_db stores the data of book_name, book_to_return and books_on_rack. Similarly, issue_db stores data like books_left_to_return, book_submitted and submission_date. Both the process uses data form data base for records and data manipulation.

We hope by this DFD you are clear the method of returning a book to the library, now you can implement this idea onto your projects. This type of model will be very helpful for the projects like Library Management System.

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