Data flow diagram also called Data Flow Diagram (DFD). Data flow diagram is use to figuring system division into smaller module. DFD can facilitate user that insufficiently understand computer's area for understanding system who will be worked.
CONTEXT DIAGRAM
Context diagram is consisting of one process and figures scope of a system. That is supreme level from DFD that figuring all input goes to system and output of system. In context diagram, stored (storage) is not available.
ZERO DIAGRAMS
Zero diagrams are use to figuring process from DFD. The diagram can giving views thoroughly concerning handled system, show function or aught main process, data flow and external entity. On this level is enabled to marks sense data storage. For a process that don't elaborated again on succeeding level then was enhanced symbol ‘*’ or ‘p’ by the end of process numbers. Balancing of input and output among zero diagram and context diagram must be maintained.
DETAILS DIAGRAM
Details diagram that describes the process what’s aught on zero diagram or level on it.
Numbering level on DFD:
| Level’s name | Diagram’s name | Process 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, ... |
SPECIFICATION PROCESSES
Each process on DFD shall have process specification. On top level method that is utilized to figure the process can by use of descriptive sentence. At more level detailed that is at lowermost process (primitive functional) requiring the specification of more structure. Specification of processes will be guidance for programmer in making program (coding). Method that is utilized in specification processes are breakdown of process in shaped story, decision table and decision tree.
EXTERNAL ENTITY
An external entity is a source or destination of a data flow which is outside the area of study or something that beyond system, but it gives data into system or gives data from system. Only those entities which originate or receive data are represented on a business process diagram. External entity is symbol with notation box. External entity is excluding part of system.
Rules for Naming:
- Terminal name as noun
- Terminal can not have a same name but the object is really same
DATA FLOW
A data flow shows the flow of information from its source to its destination. A data flow is represented by a line, with arrowheads showing the direction of flow. Information always flows to or from a process and may be written, verbal or electronic. Each data flow may be referenced by the processes or data stores at its head and tail, or by a description of its contents.
Dataflow notations:
Guideline to naming:
1. Name of Data's flow which consisting of several word's flow connected by interlocking lines
2. No data's flow which its have same name, and naming shall reflect its content
3. Data flow that consisting of several element gets to be declared with element group
4. Avoid of using word ‘ data ’ and ‘ information ’ to naming on data flow
5. As much as can the name of data flow is written completed
other rule:
· name of Data flow which turn in at a process may not same by the name of secretory data flow of that process.
· data flow that ingoing goes to or out from data storage not necessarily been given name if:
o Simple data flow and perspicuous
o Data flow figures all item's data
· there is no data flow from terminal to data storage or on the contrary because the terminal is not part of system, terminal relationship with data storage shall pass through process
PROCESS
The process is also often called bubble. Process is what does be worked by system. A process transforms incoming data flow into outgoing data flow. A process shows a transformation or manipulation of data flows within the system. Each process has one or many entries and resulting one or many outputs.
Guideline to naming processes:
* Name processes consisting of verb and noun that reflect that process function
* Don't utilize the word 'process' as part of name a bubble
* there is no many process that have same name
* Process shall be numbered. Number thread as much as can following the flow or process thread, but such number thread doesn't mean absolutely representing process thread chronologically
Process Notations
DATA STORAGE
Data storages are repositories of data in the system. They are sometimes also referred to as files. It is represented by a pair of parallel lines or two lines with one of the side open. Process can take data from or gives data to database
Guideline to naming:
· Name shall reflect data storage
· If its name more than one word then has to be hyphened
SYMBOLS USED ON DFD
DATA DICTIONARY
Data dictionary is also called with a system data dictionary is a catalog of facts and data information needs of an information system. In function to help system agent to interpreting application in detail and organization all of data element that utilized by system exactly so user and system analyst have same understanding basic about entry, output, storage and process. On analysis’s phase, data dictionary is utilized as communication device among system analyst with user. On system design phase, data dictionary is utilized to design input, reporting and database. Data flow on DFD has global character; the more detail information can be seen on data dictionary.
Data dictionary load things as follows:
· Name of data flow: must note that readers that require more explanation about a data flow can look for it squashy.
· Alias: alias or other name of data can written if available
· Data form: utilized to agglomerate data dictionary into its usage when designing of system
· Data flow: show that from where data flow and where data wend.
· Explanation: giving explanation about meaning of data flow
BALANCING IN DFD
· Data flow which it’s in and out from one process has to equal with data flow which it’s in and out from details of process on level under it.
· name of data flow which its in and out from one process must be same with the name of data flow which its in and out from details of that process
· Total and name of external entity of a process has to equal with total and name of external entity of details of that process
· Things that must be noticed on DFD who has more than one level:
o input and output balance must be available 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 from terminal on level 0, meanwhile balance among level 1 and level 2 are seen on input / output of data flow goes to / from process that pertinent
o name of data flow, data storage and terminal on every level must be same if its object is same
PROHIBITION IN DFD
· Data flow may not from external entity directly to wend another external entity without passing a process.
· Data flow may not from data storage directly goes to external entity without passing a process
· Data flow may not of direct data storage wend to another data storage without passing a process
· Data flow from one process directly to wend another process without passing an data storage is advisable/can be avoided
DIAGRAM CASH INVESTMENT DATA
There are 2 forms of DFD:
1. Physical Data Flow Diagram (PDFD), more appropriately used to describe the existing system (old system). The emphasis is how the processes of the system is applied, including manual processes.
2. Logical Data Flow Diagram (LDFD), more appropriately used to describe the system that will be proposed (new system), with no emphasis on how the system implemented, but the emphasis only on the logic of the demand system, that is what the process logic needed by the system.
GUIDELINES TO DRAWING DFD
1. Identify the first unit outside of all involved in the system. For example, sales for the system have involved external entity such as customer, credit manager, warehouse division and delivery division.
2. Identification all of input and output that involved in union with the outside.
3. Draw the context diagram (context diagram) first. DFD is a tool for structured analysis. The structure of this system to try to describe the first time the outline (called by top level) and split them into the more detailed (called by lower level) is called overview diagram (level 0). Each overview will be drawn more detailed again called level 1, and each process in level 1 will be drawn back with a detailed level with a 2 and so on until each of these processes can not be drawn again.
4. Draw the hierarchy chart for all process that is in the system first. Tiered chart (hierarchy chart) used to prepare the DFD drawing to more levels down again.
5. Draw the sketch of DFD for overview diagram (level 0) based on process on the tiered chart.
6. Draw the DFD for next level which is level-1 and so on.
7. After all of level in DFD is drawn, next is draw the DFD for management reporting which its drawn separately.
8. after all of level in DFD is drawn, and then all of this DFD can combine in one diagram.
Reference:
- ER Ngurah Agus Sanjaya. Slide Part 4 - DATA FLOW DIAGRAM.
- HM, Jogiyanto. 2007. Analisis & Desain Sistem Informasi. Yogyakarta: ANDI.
No comments:
Post a Comment