Data flow diagram or DFD used to depicting the division of system into smaller module, and can facilitate less comprehending user of computer area to understand system to be done.
Diagram Context
This diagram is diagram of level highest of DFD depicting system relation with external environment.
- Consist of one process and depicting scope from a system
- System limited by boundary ( depicted by dash line)
- There may not be any is depository ( storage)
Diagram Zero
This diagram is dekomposisi of context diagram.
- Depicting process of DFD
- Give a fully regarding system handled , showing existing especial process or function , data stream and of eskternal entity
- At this level is enabled by the existence of data of storage
- For the process which isn’t detailed again at level hereinafter hence enhanced by symbol ‘*’ or ‘ P’ by the end of process number
- Balance input and of output ( balancing) between diagram 0 with context diagram have to be looked after
Diagram Detailed
Diagram detailed to represent diagram elaborating process what there is in diagram zero or level above
- Level numbering on DFD
| NAME of LEVEL | NAME of DIAGRAM | PROSES NUMBER |
| 0 | Context | |
| 1 | Diagram 0 | 1.0, 2.0, 3.0, ... |
| 2 | Diagram 1.0 | 1.1, 1.2, 1.3, ... |
| 3 | Diagram 1.1 | 1.1.1, 1.1.2, ... |
- In one level shall not there are more than 7 process and maximal 9, if more hence must be done dekomposisi
Specification of Process
Every process at DFD have to have the specification of process. At method level top used to depict process earn by using descriptive sentence. At more level detailed that is at process most under (primitive functional) requiring the specification of more structure. Specification of process will become guidance to programmer in making program (coding). Method which is used in specification of process: breakdown of process in the form of story, table decision, tree decision.
External Unity
External unity is something that beyond system, but he give data into system or give data of system
- Symbol with notation box
- External entity not the including the part of system
Naming:
- Name of terminal in the form of noun
- Terminal may not have the name of same except its same object it is true
Data Current
Data current Represent place emit a stream of information.
- Depicted with connective straight line component of system
- Data current shown with direction bow and line called of data current emiting a stream
- Data current emit a stream of among process, data of storage and show data current of data which in the form of input for system
Data Current 2
Naming Guiding:
- Name of data stream which consist of some word stream attributed to continued line
- There may not be any data stream which its same name and giving of name have to express its contents
- Data stream which consist of some element can be expressed with element group
- Avoid usage of word ‘ data’ and ‘ information’ to give the name at data stream
- As possible the name of data stream written is complete
Data Current 3
Other Rule:
- Name of data stream which come into a process may not is equal to name of secretory data stream of process
- Data of flow which step into or go out from data of storage needn't be called by if:
- Comprehended easy and simple data stream
- Data stream depicting all data item
- There may not be any data stream of terminal to data of storage or on the contrary because terminal non part of system, terminal relation with data of storage have to through process
PROCESS
Process represent what done by system, process can process data stream or data enter to become exit data stream.
- The process fucntion is transform one or some data become one or some output data as according to specification of which is wanted
- Every process have one or some input and also yield one or some output
- Process often is also referred as by bubble
Guidance giving process name:
- Name of process consist of noun and vb. expressing process function
- Don't use word process as part of the name of a bubble
- There may not be any some process owning the name of is same
- Process have to give number. Number sequence as possible follow process sequence or stream, but that way meaningless number sequence absolutely represent sequence process chronologically
DATA DEPOSIT
Data of Storage represent existing data repository in system. Symbol with a couple of parallel line or two line wrongly one side from other side openly. Process can take data from or give data to database.
- Naming Guiding:
- Name have to express data of storage
- If the name more than one word hence have to say the word to joint
SYMBOL DATA
DATA DICTIONARY
Function to assist perpetrator of system to interpret application in detail and organizational all used by data element is system precisely so that user and system analyst have is same congeniality base about input, output, depository and process. At analysis phase, data dictionary used as by communication means between system analyst with user. At phase scheme of system, data dictionary used to design input, database and report. Data current at DAD have the character of globally, boldness more detailed can be seen by at data dictionary.
Data dictionary load the followings:
- Name of data current: have to be noted reader to needing furthermore clarification about a data current can look for it easily
- Alias: name or alias of differ from data can be written if there are any
- Data form: used to group data dictionary into its use time scheme of system
- Data current: showing where from data emit a stream of and where data go to
- Clarification: giving clarification about meaning of data current
BALANCING IN DFD
Data stream which come into and go out from one process have to is equal to data stream which come into and go out from detail of process at level / under level. Name of data stream which come into and go out from one process have to is equal to name of data stream which enter into and go out from detail of process. Amount and name of entitas external from a process have to is equal to name and amount of entitas external from detail of process.
- Things which must be gave attention to DFD owning more than one level:
- Have to there are input balance and of output between one and level of level next
- Balance between level 0 and level 1 seen at input / output of data stream to or from terminal at level 0, while balance between level 1 and level 2 seen at input / output of data stream to / from pertinent process
- Name of data stream, data of storage terminal and at every level have to be is same if its is same object
PROHIBITION ORDER IN DFD
- Data current may not from direct external entitas go to other external entitas without passing a process
- Data current may not from direct data deposit go to external entitas without passing a process
- Data current may not from direct data deposit go to other data deposit without passing a process
- Data current from one direct process go to other process without passing a data deposit better / can possible avoided
Refference:
ER Ngurah Agus Sanjaya. Slide Part 4 - DATA FLOW DIAGRAM
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