Data Flow Diagram (DFD)
I. Data Flow Diagram (DFD)
- Describe the division of system in a smaller modul.
- To make easier a user, who is don't understand a computer aspect to be understanding the system.
II. Context Diagram
- Consist of a process and drawing a scope of a system.
- That is highest level of DFD, which it is drawing all of input to system and output of system.
- System limited by boundary (is depicted by dash line).
- No storage.
III. Zero Diagram
- Describe the process from DFD.
- Perhaps in this level can be storage data.
- For a process, which not dividing again in next level, so we can add symbols '*' or 'P' in the last process numbers.
- Balancing of input and output between zero diagram and context diagram have to be looked after.
IV. Detail Diagram
- That is a diagram, that loosen all process in zero diagram or level before.
- Numbering level in the system.
- In a level, should nothing more than 7 process and maximal 9, if more that it, so we must decomposising.
V. Specification of Process
- Every process in DFD, must have process specification.
- In top level method, that is we use for drawing a process with descriptive sentence.
- At more level detailed, that is in underneath process (functional process) need specification, that is more structured.
- Specification of process will be guidance for programmer to make program.
- The method, which we use in specification process : analysis of process in a story, decision table, decision tree.
VI. External Unity
- A something, that is in external system, but it is giving a data to system or giving data from system.
- The symbol is notation box.
- External entity is not a part of system.
- Naming :
a. The form is terminal's name is noun.
b. Terminal not have a same name, except the object in same.
VII. Data Flow
- Is a information's place.
- The symbol is a line, that is to combine a component of system.
- Data flow shown with direction bow and line, given name or data flow poured.
- Data flow poured between process, data storage and showing data flow from data, that is input for system.
- Guidance of giving of name.
a. The name of data flow, consist of some words flow to combine with continued line.
b. No data flow, which the name is same and gifting name must reflecting the containts.
c. Data flow, the consist of some elements can be expressed with group element.
d. Avoid usage of word ‘ data’ and ‘ information’ to give the name of at data flow.
e. As possible the name of data stream written is complete.
- Other rule.
a. Data flow name which turn in at a process may not same by the name of secretory data flow of that process.
b. Data flow which step into or go out from data of storage needn't be called by, if :
b.1 A comprehended easy and simple data flow.
b.2 Data flow describe all data item.
c. No data's flow 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.
VIII. Process
- Process is what done by system.
- The function of process is transformation one or some input data become one or some output data as according to specification
of which is wanted
a. Every process have one or some input and producing one or some output.
b. The process is buble.
- Director for gifting the name of process.
a. Name process consist of verb and noun, which it reflecting that function of process.
b. Don't use word process as part of name of a buble.
c. No some process, that have the same name.
d. Process must to give number. Serial number must following the current or serial process, but serial number is not absolute
that is serial process with chronologys.
IX. Data Storage
- Data storage is a storage data's place in system.
- That symbol is a pair of parallel line or two line with one of side.
- Process can take data from or giving data to database.
- Director for gifting the name.
a. The name must reflect data storage.
b. If its name more than one word, so must giving continued sign.
X. DFD Symbol
XI. 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 and user.
- At phase scheme of system, data dictionary used to design input, database and report.
- Data current at DFD have the character of globally, boldness more detailed can be seen at data dictionary
- Data dictionary contain the followings :
a. Name of data flow : must to be noted reader to needing furthermore clarification about a[n data current can look for him easily.
b. Alias : alias of data can be written.
c. Data form : used to group data dictionary.
d. Data flow : showing where from data emit a stream of and where data heading.
e. Explanation : giving clarification about meaning of data current.
XII. Balancing in DFD
- Data flow which come in and out from one process must be same with the data flow which come in and out from specification process at
the level beneath.
- The name of data flow which come in and out from one process must be same with the name of data flow which come in and out from that
specification process.
- Totals and names of the external entity from one process must be same with totals and names of the external entity of that specifica-
tions process.
- Things that must be attended in DFD which has more than one level is :
a. There's must be input and output balancing between one level and the next levels.
b. Balancing between level 0 and level 1 is seen in input/output of the data flow to or from zero level terminal, meanwhile balance
between level 1 and level 2 is seen in input/output of the data flow to or from the process it self.
c. The name of data flow, data storage, and terminal in each levels must be same if their object are same.
XIII. Prohibition in DFD.
- The data flow may not directly from one external entity to another external entity without any process.
- The data flow may not directly from data storage to external entity without any process.
- The data flow may not directly from data storage to the other data storage without any process.
- The data flow from one process directly go to another process without any data storage should be avoided.
Ref :
Prof.Dr Jogiyanto HM,MBA,Akt. Analisis dan Desain. Penerbit Andi: Yogyakarta 2005
ER Ngurah Agus Sanjaya, S.KOM, M.KOM. Slide Part 4 - DATA FLOW DIAGRAM
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