1 / 14

IT Systems Analysis and Design

IT Systems Analysis and Design. SSADM – Design. Aims. Learn about Data Flow Diagrams (DFDs) and what they are used for. Be able to create context DFD and Level one DFD Gain an insight into further levels of detail (DFD). Data Flow Diagrams. DFD

jonah-clements
Télécharger la présentation

IT Systems Analysis and Design

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. IT Systems Analysis and Design SSADM – Design Btec National - IT SYSTEMS ANALYSIS AND DESIGN

  2. Aims • Learn about Data Flow Diagrams (DFDs) and what they are used for. • Be able to create context DFD and Level one DFD • Gain an insight into further levels of detail (DFD) Btec National - IT SYSTEMS ANALYSIS AND DESIGN

  3. Data Flow Diagrams • DFD • Data flows are used to show how a system will/does operate. • They show how the data flows around the system. Btec National - IT SYSTEMS ANALYSIS AND DESIGN

  4. Data Flow Diagrams • DFD • Data flow diagrams show the system boundary, the external entities, the processes and the data stores. Btec National - IT SYSTEMS ANALYSIS AND DESIGN

  5. Data Flow Diagrams • External entities – things outside the system, such as people, organisations and other systems Customer Btec National - IT SYSTEMS ANALYSIS AND DESIGN

  6. Unique ID Calculate Benefit 1.3 Process description Data Flow Diagrams • Process, should always start with an active verb. The number in the corner is used to identify the parent process and to uniquely identify this process. Btec National - IT SYSTEMS ANALYSIS AND DESIGN

  7. Customer Details D8 Unique ID Data store name Data Flow Diagrams • Data Store • This is used to store and retrieve data from, these are not shown at level 0 (context diagram) Btec National - IT SYSTEMS ANALYSIS AND DESIGN

  8. Customer address Data Flow Diagrams As in Yourdon diagrams, a flow is shown by a line with a flow name and an arrow at the destination end, e.g. • The data flow name must be a noun (i.e. a thing not an activity) • Data flows may only go: between two processes; between an entity and a process; between a data store and a process. • Data flow lines don’t merge or split (but more than one line can go to/from the same entity, process or data store) • Data flows must not cross (use duplicate entities and/or data stores to avoid crossinglines) Btec National - IT SYSTEMS ANALYSIS AND DESIGN

  9. Data Flow Diagrams • Context Diagram • A context diagram is the highest level DFD (general overview), it shows the data flows, external entities, the process (system in focus, don’t be tempted to divide the process into too many steps or the diagram will become too complicated) Btec National - IT SYSTEMS ANALYSIS AND DESIGN

  10. Customer 1 Create Booking Data Flow Diagrams • Context Diagram (high level) – Example (Notice no data stores) Booking details Booking confirmation Btec National - IT SYSTEMS ANALYSIS AND DESIGN

  11. Data Flow Diagrams • Moving from high-level to low-level • The high level DFD needs to be broken down into more detail (decomposed) to produce a low-level DFD. • The first step is to divide the identified process in the context DFD into several, more detailed processes. • This is generally performed by using the information gathered so far to determine what the divided processes should be. • Some analysts say as a rule of thumb there should be a single process dealing with each data flow attached to an external entity. Btec National - IT SYSTEMS ANALYSIS AND DESIGN

  12. Customer Customer D2 Customer Details 1.1 Check Availability 1.2 Record new booking 1.3 Confirm booking Room booking details Booking details D1 Room Booking Details Availability details Booking details Customer details Customer details Booking confirmation Btec National - IT SYSTEMS ANALYSIS AND DESIGN Notice the system boundary

  13. Data Flow Diagrams • Moving from Level 1 to Level 2 • A level 1 may need breaking down again into further processes i.e. if the confirm booking process (1.3) was complicated then that process could be broken down further to detail the complexities. The process IDs would start with 1.3.1, 1.3.2 etc. • This would continue until the analyst is satisfied that he/she has a clear understanding. Btec National - IT SYSTEMS ANALYSIS AND DESIGN

  14. Conclusion • Learned about Data Flow Diagrams (DFDs) and what they are used for. • We created context DFD and Level one DFD • Gained an insight into further levels of detail (DFD) Btec National - IT SYSTEMS ANALYSIS AND DESIGN

More Related