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Data Flow Diagrams

Data Flow Diagrams. Introduction for organizers. The Problem. How to model a system before building or changing it. Build an Abstraction. Molecular Model. Life Cycle. What Life Cycle?. What does it do? All or Part? Build or Buy?

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Data Flow Diagrams

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  1. Data Flow Diagrams Introduction for organizers

  2. The Problem • How to model a system before building or changing it

  3. Build an Abstraction • Molecular Model

  4. Life Cycle

  5. What Life Cycle? • What does it do? • All or Part? • Build or Buy? • Early decision for all software systems are whether to build or buy • WHO works on it? • WHO will run it? • HOW Long will it last?

  6. Symbol of never-ending life The Software Development Cycle • Identify problems, opportunities and objectives. 9. Maintain the system 10. Evaluate and Plan for New Versions 8. Deploy 2. Define Information Requirements 7. Train 3. Analyze Detailed Needs 6. Install and Test 4. Specify or Design the Recommended System 5. Buy or Develop the Software

  7. Different Points of View Databases CPU’s Operating Systems Winning Campaigns

  8. Put the Parts Together Technology Organization’s Requirements User Experts Technical Experts

  9. Who Does What? User Expert Technical Assistance Provider Joint Effort

  10. Who Does What? User Expert Technical Assistance Provider Joint • Identify problems, opportunities and objectives. 9. Maintain the system 10. Evaluate and Plan for New Versions 8. Deploy 2. Define Information Requirements 7. Train 3. Analyze Detailed Needs 6. Install and Test 4. Specify or Design the Recommended System 5. Buy or Develop the Software

  11. Data Flow Diagram Parts • External Entity • Process • Data Flow • Data Store

  12. Funder Politician Allies General Population Constituency Government External Entity The External Entity symbol represents sources of data to the system or destinations of data from the system.

  13. Signup Member Plan campaign Communicate message Pay Bills Process The Process symbol represents an activity that transforms or manipulates the data (combines, reorders, converts, etc.).

  14. All Data Flows are defined in a data dictionary Data Flow The Data Flow symbol represents movement of data.

  15. Data Store The Data Store symbol represents data that is not moving (delayed data at rest).

  16. Procedure • Start at the top level with external entities to organization • Create a context diagram with system at center and external entities sending and receiving data flows;

  17. Context Diagram

  18. Carry Entities and Data Flows Forward

  19. Level 1 • CLO Example

  20. Level 1 • CLO Example

  21. Exercise

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