Presentation on theme: "CAPE INFORMATION TECHNOLOGY – Unit 2"— Presentation transcript:
1 CAPE INFORMATION TECHNOLOGY – Unit 2 INFORMATION MANAGEMENTUnit 2 SO 6Data Flow Diagramsdescribe data flow diagrams (DFD);Define DFD; identify and describe the four symbols (elements): entity, process, data store, data flow; identify and describe the various levels of DFDs including context level DFD and first level detailed DFD.
2 What are Data Flow Diagrams (DFDs)? A Data Flow Diagram (DFD) is a graphical representation of the "flow" of data through an Information System. It differs from the as it shows the flow of data through processes instead of hardware.A Data Flow Diagram can also be used for the visualization of data processing (structured design).Data flow diagrams were invented by Larry Constantine, the original developer of structured design, based on Martin and Estrin's "data flow graph" model of computation
3 Data Flow Diagrams (DFDs) Data flow diagram (DFD) is a picture of the movement of data between external entities and the processes and data stores within a system
14 Source/Sink (External Entity) External entity that is origin or destination of data (outside the system)Is the singular form of a department, outside organisation, other IS, or personLabels should be noun phrasesSource – Entity that supplies data to the systemSink – Entity that receives data from the system
15 Rule: Source/SinkMust be connected to a process by a data flow
17 Rules for Using DFD Symbols Data Flow That ConnectsYESNOA process to another processA process to an external entityA process to a data storeAn external entity to another external entityAn external entity to a data storeA data store to another data store
19 Context Diagram Top-level view of IS Shows the system boundaries, external entities that interact with the system, and major information flows between entities and the system.Example: Order system that a company uses to enter orders and apply payments against a customer’s balance
21 Level-0 DFDShows the system’s major processes, data flows, and data stores at a high level of abstractionWhen the Context Diagram is expanded into DFD level-0, all the connections that flow into and out of process 0 needs to be retained.
24 Lower-Level Diagrams Functional Decomposition Balancing An iterative process of breaking a system description down into finer and finer detailUses a series of increasingly detailed DFDs to describe an ISBalancingThe conservation of inputs and outputs to a data flow process when that process is decomposed to a lower levelEnsures that the input and output data flows of the parent DFD are maintained on the child DFD
25 Strategies for Developing DFDs Top-down strategyCreate the high-level diagrams (Context Diagram), then low-level diagrams (Level-0 diagram), and so onBottom-up strategyCreate the low-level diagrams, then higher-level diagrams