DATA FLOW DIAGRAM

April 5, 2009 at 3:14 am (Tidak terkategori)

Data flow diagram illustrate how data is processed by a system in terms of inputs and outputs, describe the distribution of the modules in the system to a smaller .Easy to understand the less the field to understand the computer system that will be done. Data flow diagrams can be used to provide a clear representation of any business function. The technique starts with an overall picture of the business and continues by analyzing each of the functional areas of interest. This analysis can be carried out to precisely the level of detail requird. The technique exploits a method called top-down expansion to conduct the analysis in a targeted way.

A data-flow diagram use to make easy delineation a system a new one that will be developed logically without care physical environmentally where that data is adrift or environmentally physical where that data will be kept, therefore we utilize Flow’s Data or Data flow diagram diagram. Diagram grooves data constitute tool that adequately popular present, since gets to figure data current in a system with most structure and is clear, that is why DFD constitute the most assistive tool necessary for a system analyst. DFD purpose as tool of system display popularized by Tom DeMarco (1978) and Gane & Sarson (1979) by use of analisis sitem’s method approaching most structure (structured system analysis method). DFD that figured can auto and also manual system by use of image which gets graph network form.

Data-Flow Diagram (DFD)

· Also Called Data Flow Diagram (DFD)

· Figuring system division into smaller module

· Making user that have no a lot of knowledge of computer for understands system who will be develop

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Data Flow Diagram Consisting of:

1. Context Diagram:

· Consisting of one process and figures scope of a system

· Constituting supreme level from DFD that what does figure all input that goes to system and output of system

· System drew the line by boundary (figured by dotted line)

May not there is stored (storage)

1. Zero Diagram

· Describe the process of the DFD

· Provide views on the overall system in which, showing the main function or process that is, the flow of data and entity eskternal

· At this level of data storage possible

· For processes that do not detailed again on the next level then added the symbol ‘*’ or ‘P’ at the end of the process

· Input and output balance (balancing) between 0 to diagram context diagram should be maintained

2. Detail Diagram

· Decompose a process that is in the diagram zero level or above

· In the one level there should be no more than 7 units and the maximum of 9, when more should be done in the decomposition

· Each process in the DFD must have a specification process

· At the top level method is used to describe the process can use a sentence with descriptive

· On a more detailed level, namely on the bottom (functional primitive) requires specification of a more structuredspecification process will be the guideline for the programmer to make this program (coding)

· Methods used in the specification process: the process of disintegration in the form of a story, decision table, decision tree

3. Process Spesification

· Each process on DFD must have process specification .

· On top level methodics that is use to figure process can by use of descriptive sentence

· On more detail level which is on lowermost process (functional primitive) needing more structure specification .

· Specification processes will be guidance for programmer in make a program (coding)

Method that is utilized in specification processes: breakdown of process in shaped story, table decision , tree decision.

4. Outer Unity

· Something system outboard, but it gives data into system or gives data of system

· Notation with notation box

· External entity excluding part of system

· Naming: Terminal name as substantive as Terminal may not have same name excepts the same object.

5. Data Flow

§ It is a place flowed the information

· described the straight line that connects the components of the system

· Flow data is shown with the direction arrows and the name on the flow of data that flows

· Flow data flow between processes, data storage and data flow indicates that the form of data input for the system

· Guidelines of the name:

1. Name of the flow of data that consists of some words associated with the flow lines connect

2. No flow data for the same and the name should reflect its content

3. The flow of data that consists of several elements can be expressed with the group element

4. Avoid using the word ‘data’ and ‘information’ to give a name to the flow of data

5. Wherever possible the complete flow of data is written

§ Terms of others:

1. Name of the flow of data into a process may not be the same as the name of the data flow out of the process

2. Data flow into or out of data storage does not need to be given a name if: Flow of data simple and easy to understand, Flow of data describing all the data items

3. There can be no flow of data from the terminal to the data storage, or vice versa because the terminal is not part of the system, the relationship with the terminal data storage must be through a process

Name application guidance:

· Data streaming name which consisting of umpteen flow word to be linked by interlocking line

· May not there is streaming data which its same name and name application shall reflect its content

· Data flow that consisting of umpteen element gets to be declared for by element group

Other rule:

· Data streaming name which turn in at a process may not same by the name of secretory data flow of that process.

· Flow’s data in or out from storage’s data not necessarily been given name if:

§ Simple data flow and perspicuous

§ Data flow figures all item’s data

· May not there is streaming data of terminal go to storage’s data or on the contrary since terminal is not part of system, terminal relationship with data storage shall pass through process

6. Process

· Process constitutes what do be worked by system

· Process can process data or input data flow become data flow come out

· Process functioninging to transform one or many entry data become one or many output data correspond to desirable specification

· Each process has one or many entries and resulting one or many outputs

Frequent process is called bubble.

Name application guidance processes:

· Name processes consisting of job and noun word that reflect that process function

· Don’t utilize process word as part of name a bubble

· May not there is many process that have same name

· Process shall numbered. Number thread as much as can follow flow or process thread, but such number thread doesn’t mean absoluting to constitute chronological process thread .

Data Storage:

· Storage’s data constitute aught data repository in system

· Is figured with a couple equal line or two line with incorrect single-sided sideways exposed

· Process can take data from database or insert data to database

· Name application guidance:

o Name shall reflect storage’s data

o If its name more than one word therefore has to be hyphened

DFD Symbol:

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· Data flow that turns in and out from one process must equal data flow that turns in and out of details of process on level / level under it

· Data streaming name which turn in at and out from one process must have with by the name of data flow that turns in at out from details of that process

· Total and entitas’s name extern of a process must to equal total and entitas’s name extern of details of that process

· Things who shall be noticed on DFD who has more than one level:

o Shall available input balance and output among one level and next level

o Balance among level 0 and level 1 is seen on input / output of data flow goes to or of terminal on level 0, meanwhile balance among level 1 and level 2 are seen on input / output of data flow goes to / of process that pertinent

o Data streaming name, storage’s data and terminal on every level shall same if its object with

Prohibition in DFD

· Data flow may not from extern entity directing to another extern entity without via a process

· Data flowt may not from direct data trove make towards extern entity without via a process

· Data flow may not of direct data trove wend another data trove without via a process

Data current of one process directing to wend another process without via an advisable data trove or maybe can be avoided.

DFD Example:

3

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