Computer Sciene of Udayana State University

April 5, 2009

Data Flow Diagram Levels

Filed under: Computer Science — ignaga @ 1:58 AM

Context Level Diagram

This level shows the overall context of the system and its operating environment and shows the whole system as just one process. It does not usually show data stores, unless they are “owned” by external systems, e.g. are accessed by but not maintained by this system, however, these are often shown as external entities

context level diagram

context level diagram

Level 1 (High Level Diagram)

This level (level 1) shows all processes at the first level of numbering, data stores, external entities and the data flows between them. The purpose of this level is to show the major high-level processes of the system and their interrelation. A process model will have one, and only one, level-1 diagram. A level-1 diagram must be balanced with its parent context level diagram, i.e. there must be the same external entities and the same data flows, these can be broken down to more detail in the level 1, e.g. the “enquiry” data flow could be spilt into “enquiry request” and “enquiry results” and still be valid.

Level 1 (High Level Diagram)

Level 1 (High Level Diagram)

Level 2 (Low Level Diagram)

This level is a decomposition of a process shown in a level-1 diagram, as such there should be a level-2 diagram for each and every process shown in a level-1 diagram. In this example processes 1.1, 1.2 & 1.3 are all children of process 1, together they wholly and completely describe process 1, and combined must perform the full capacity of this parent process. As before, a level-2 diagram must be balanced with its parent level-1 diagram.

Level 2 (Low Level Diagram)

Level 2 (Low Level Diagram)

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8 Comments »

  1. All 3 diagrams well illustrated and well explained.Found them also attarched in waki, very intresting.

    Comment by DUNCAN KAMAU — June 24, 2009 @ 8:25 PM | Reply

    • thanks duncan for the comment, i am sorry that i very late to reply your comment.

      Comment by ignaga — August 31, 2010 @ 11:56 AM | Reply

  2. I LOVE THIS WEBSITE SO MUCH

    Comment by Ian Welch — March 29, 2010 @ 12:03 PM | Reply

    • thanks ian for the comment, i am sorry that i very late to reply your comment.

      Comment by ignaga — August 31, 2010 @ 11:53 AM | Reply

  3. I LOVE THIS COMMENT IAN WELCH

    Comment by Stevo Holton — March 29, 2010 @ 12:09 PM | Reply

    • thanks stevo for the comment, i am sorry that i very late to reply your comment.

      Comment by ignaga — August 31, 2010 @ 11:59 AM | Reply

  4. Organized. Simple. Exactly what I need to know!

    THANK YOU!

    Comment by AL — March 10, 2011 @ 8:20 PM | Reply

    • Yeah thanks AL, i’m really proud with your comment. i will continue writing this blog in next month, because i will work in a software house and i will publish what i have learn there. Thank you AL for the comment.

      Comment by ignaga — March 12, 2011 @ 1:04 AM | Reply


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