Saturday, October 27, 2012
Friday, September 28, 2012
- Correctness checking determines that the syntax and connections used in diagrams, charts, and so forth are accurately used.
- Completeness checking is performed with the users to validate the meanings of all terms and to verify the semantics used in all documentation.
- Consistency checking ensures consistency and correctness of all entries that span multiple diagrams, text, charts, and so on. Consistency checks evaluate the interitem syntax and semantics. These checks are first performed by the project team during walk-throughs or other quality assurance evaluations. Then, they may be reviewed by independent quality assurance analysts as an added check.
Sumber: Conger, 2008
For each Level 0 process,
- Draw the input and output flows and the icons to which they connect from the higher level diagram. This forms the skeleton of the diagram. These are called the net inflows and outflows.
- Define the subprocesses by asking, "What are the steps required to do this process?" Then for each step, "Can I separate this from the other steps and do it in isolation?" For each subprocess you isolate, draw a process rec-tangle on the lower level diagram.
- Identify whether data stores are required or not. Add them and, if they are new, name them.
- Identify data flows to complete the diagram. Make sure you provide all and only the information required to perform the process.
- Review the diagram for unnecessary connec-tions and, if found, remove them.
- Update the data dictionary with all new information.
Sumber: Conger, 2008
Friday, September 21, 2012
- Identify the Level 0 processes that are within the circle of the context diagram, without defining any data stores.
- The difficulty of this activity varies with your understanding of the problem domain and the scope of the project.
- After the processes are identified, next define file locations on the Level 0 data flow diagram.
- You could leave files for a lower level of analysis as many texts and companies do by convention. In that case, you are ready to draw the diagram.
- To identify data stores, first consider each process.
- Can the process be completed without reading or writing to a data store?
- If your answer is yes, then you do not need a file at this level.
- If the answer is no, you need one data store for every required read action and every required write action.
- Many times, the reads and writes are to the same data store. Then, you have one data flow per input/output action.
- As these required reads and writes are identified, you add to the DFD to include the data store name and data flow(s).
- When you do this part of the drawing, make sure that each flow and store has a name.
Level 0 Syntax Rules:
- All processes are connected to something else.
- All process have both inputs and outputs.
- No processes have only outputs or only inputs.
- Processes may connect to anything: other processes, data stores, or entities.
- All processes have a unique name and number.
- Each process number is used once in the diagram set.
- Only subprocesses of a process shall follow the numbering scheme of the parent process.
- Entities and data stores may connect only to processes. Another way to state this is that each data flow must have at least one end connected to a process.
- Data flows are the only legal type of connection between entities, processes, and data stores.
- Make sure there are no dangling arrows.
- The net data flows to and from context diagram external entities must balance, that is, be present, in each level of DFDs.
- Trivial errors and exceptions are not handled until L1 or lower in the DFD set.
- Trivial data stores show up in the diagram set the first time they are referenced by a process.
Sumber: Conger, 2008
Friday, September 14, 2012
- A data flow diagram (DFD) is a graphic representation of the application's component parts.
- The entities and data flows from the context diagram are all present ini DFD.
- Data flows may connect processes to other processes, data stores, or external entities.
- Data stores and external entities do not interact directly with each other.
- All entities and data flows from the higher level processes must be in every more detailed diagram. The names of entities and data flows must be consistent across the levels of the diagrams
- Define the processes.
- Define the files and other data flows required to support the processes.
- Draw a Level 0 DFD. At level 0, ignore trivial error paths and data stores. If you define a validation process, you must eventually identify an error path. Define the error path at the primitive level. Similarly for data stores, define files when they are shared between processes. Introduce files that are only used within a given process at the level at which the file is shared between two or more subprocesses.
- Balance the DFD with the context diagram. Compare the net inputs and outputs to external entities on the DFD to the net inputs and outputs on the context diagram. There should be a one-to-one correspondence between the diagrams.
- Iterate through this procedure until the primi-tive level of DFD is reached for all processes. Always balance the current level DFD's net inputs and outputs with those of the previous level.