DFD Quis

”Data Flow Diagram”

data-flow diagram (DFD) is a graphical representation of the "flow" of data through an information system. It differs from the flowchart as it shows the data flow instead of the control flow of the program.

Data-flow diagrams (DFDs) are one of the three essential perspectives of the structured-systems analysis and design method SSADM. The sponsor of a project and the end users will need to be briefed and consulted throughout all stages of a system's evolution. With a data-flow diagram, users are able to visualize how the system will operate, what the system will accomplish, and how the system will be implemented. The old system's dataflow diagrams can be drawn up and compared with the new system's data-flow diagrams to draw comparisons to implement a more efficient system. Data-flow diagrams can be used to provide the end user with a physical idea of where the data they input ultimately has an effect upon the structure of the whole system from order to dispatch to report. How any system is developed can be determined through a data-flow diagram.

Is a diagram illustrating the system into smaller modules, which facilitate users with less understanding to understand the field of computer systems that will be done consists of a process and describe the scope of a system

context diagram

Diagram characteristics of context are:

· Consists of a process and describe the scope of a system,

· It is the highest level of the DFD that describes the entire system to input and output of the system,

· The system is limited by Boundary (depicted by broken line),

· No storage (storage).

Zero Diagram

Depicting process of DFD, Opening on to by totally about system handled, showing existing especial process or function, data stream and of external entity, At this level is enabled by the existence of data of storage, For process which is not detailed again at level hereinafter hence enhanced by symbol '*' or ' P' by the end of process number, Input balance 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 him.

In numbering of DFD, one level shall not there are more than 7 process and maximal 9, when more hence must be done decomposition.

SPECIFICATION OF PROCESS

Every process at DFD must 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 process most under ( primitive functional) requiring the specification of more structured. Specification of process will become guidance to programmer in making program ( coding). Method which is used in specification of process is the breakdown of process in the form of story, table decision, tree decision.

External Unity

External Unity is something that beyond system, but that give data into system or give data of system.

External Unity have symbol with notation box. External in this case entity, are not the including the part of system.

Naming:

· Name of terminal in the form of noun.

· Terminal may not have the same name, except its have same object its true.

DATA CURRENT

1. Representing place emit a stream of information [him/it].

2. Depicted with connective straight line of component of system.

3. Data current shown with direction bow and line called of data current emiting a stream of.

4. 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.

Guidance of giving name:

1. Name of data stream which consist of some word stream attributed to continued line.

2. There may not be any data stream which is same name and giving of name have to express its contents.

3. Data stream which consist of some element can be expressed with element grup.

4. Avoid usage of word ‘ data’ and ‘ information’ to give the name of data stream.

5. As possible the name of data stream written is complete

Another Rule:

1. Name of data stream which come into process may not same of name the output.

2. Data of Flow which step into or go out from data of storage needn't be called when:

· comprehended easy and simple Data stream

· Data stream depict entire/all data item

3. 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 pass the process

Process

· Process represent what done by system.

· Process can process data stream or data enter to become exit data stream.

· Functioning process of transform one or some input 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 by bubble

Guidance of giving of the 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[n bubble

· There may not be any some process owning the name of same

· Process have to give by number. Number sequence as possible follow process sequence or stream, but that way meaningless number sequence absolutely represent sequence process chronologically

Data Storage represent existing data repository in system.

1. Symbol with a couple of parallel line or two line wrongly one side from other side openly.

2. Process can take data from or give data to database.

3. Guidance giving of name:

· Named have to express data of storage.

· If its name more than one word hence have to say the word to joint.

Data dictionary

· Function to assist perpetrator of system to interpret application in detail and organizational all used by data element system precisely so that user and system analyst have 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 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[is differ from data can be written by 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 at DFD

1. Data stream which come into and go out from one process have to equal to data stream which come into and go out from detail of process at level / level below/under it.

2. Name of data stream which come into and go out from one process have to equal to name of data stream which enter into and go out from detail of process

3. Amount and name of entity external from a process have to equal to name and amount of entity external from detail of process

4. Things which must be gave attention to DFD owning more than one level:

· Have to there are input balance and of output [among/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 every level have to be same if its have same object.

Prohibition order in DFD

1. Data current may not from direct external entity go to other external entity without passing the process.

2. Data current may not from direct data deposit go to external entity without passing the process.

3. Data current may not from direct data deposit go to other data deposit without passing the process

4. Data current from one direct process go to other process without passing the data deposit , it can possible to avoided.

Reference:

ER Ngurah Agus Sanjaya. Slide Part 4 - DATA FLOW DIAGRAM.

Wikipedia. Link: Data_flow_diagram.htm

Parno, SKom., MMSI. Data Flow Diagram