DATA FLOW DIAGRAM (DFD)
Definition:
DFD often being utilized to figure a system has already there is or new system that will be developed logically without considering physical environment where the data flow (e.g. telephonic, letter etcetera) or physical environment where the will be save (e.g. file card, micro filhe, hard disk, tape, floppy disk, etc).
Data Flow Diagram (DFD) are constitute applicable assistive tool to figure information data flow and process of data, begun from data inclusion until results output .
DFD constitutes tool who will be utilized on systems developmental methodology which most structure (structured analysis and design).
There is even symbol Data Flow Diagrams:
- External Entity
- Process
- Data flow
- Data Storage
CONTEXT DIAGRAM
System Context Diagram are diagrams used in systems design to represent all external entities that may interact with a system. This diagram pictures the system at the center, with no details of its interior structure, surrounding by all its interacting systems, environment and activities. The objective of a system context diagram is to focus attention on external factors and events that should be considered in developing a complete set of system requirements and constraints.
System context diagram are related to Data Flow Diagram, and show the interactions between a system and other actors with which the system is designed to interface. System context diagrams can be helpful in understanding the context which the system will be part of.
Context diagrams are used early in a project to get agreement on the scope under investigation. Context diagrams are typically included in a requirements document. These diagrams must be read by all project stakeholders and thus should be written in plain language, so the stakeholders can understand items within the document.
ZERO DIAGRAM
- Figuring process from DFD
- Giving view thoroughly about handled system, pointing out function or aught process main, data flow and external entity
- On this level is enabled marks sense data storage
- To process that don't elaborated again on succeeding level therefore enhanced symbol ‘ * ’ or ‘ p ’ at the early process numbers
- Balancing input and output (balancing) among diagram 0 by context diagram shall be petted
DETAIL DIAGRAM
- Detail diagram that describes to process what aught diagrammatically zero or level on it
- Numbering level on DFD:
- In one advisable level has no is more than 7 processes and maximal 9, if more therefore has to be done by decomposition
SPECIFICATION OF PROCESS
1. Each process on DFD shall have process specification
2. On top level method that is utilized to figure process can by use of descriptive sentence
4. Specification processes will be guidance divide programmer in makes program (coding)
5. Method that is utilized in specification of processes: b reakdown of process story type, decision table, decision tree
EXTERNAL ENTITY
Outer unity / system bounds( external entity / boundary), constituting unity at environment outer system can as person, organization or another system those are on environmentally extern will give input or accepts output of system. one that included outer unity amongst those:
- An office, department or division in corporate but system open air, which is developed.
- Person or a group person at organization but outside sys tem which being developed.
- An organization or person of outside organization as e.g. subscription, provider.
- Outdoor other information system, system being developed.
- Original source of a transactions
- Receiver a stop to a resulting reporting by system.
External entity symbol is:
Picture1. External entity notation at DFD
DATA FLOW
Symbol with the dart, where is data flow is flow between process, data trove. This data flow point out current of data who can as entry for system or result of system process and gets to get form as follows:
- Form or document that utilized by firm
- Resulting published reporting system
- Output at computer screen
- Entry for computer
- Utterance communication
- Letter or memo
- Data that is read or is recorded at file
- A noted stuffing on agenda book
- Data transmission of a computer goes to other computer
Advisable data flow given by clear name and too have mean. Name of data flow is set inside and above its arrow line.
Picture2. Data flow that is flow from customer external entity go to process of customer order is by the name of customer order.
Inside draw data flow at DFD needs to be noticed many concepts that needs. This following is concept of data flow that needs to be noticed.
1. Concept packet of data, if two or more data are adrift from sources is same to the point same therefore have been looked on data flow one and only.
Example of Data flow which is false:
Example of Data Flow which is true:
If two data this will be handled by two disparate process, mean have a purpose that different, although its source of equal, therefore in draw as following been:
2. Diverging data flow, there is diverging data flow points out a number c.c. of data flow is same of same source to the point that different.
3. Converging data flow, data flow that converging points out many data flow that variably of source that variably jointly making for to the point same.
4. Source and to the effect concept data flow, All flow shall be resulted of is data process or making towards process (can one of or the two, which is process makes towards is not process or come from is not process to make towards process or comes from process and making towards process). This is important concept because flow is either one result's data process or will be utilized to do a process.
PROCESS
Process is activity or job that did by person, machine or computer of result a data flow that turns in at to process to been resulted data flow that will come out from process. Process function 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 may be called by bubble
To physical data flow diagram (PDFD), process can be done by person, machine, or computer, meanwhile for logical flow's data diagram (LDFD), a process just point out process from computer. Process can be pointed out by symbol circle or with symbol length foursquare straightening with its dull angle.
Picture3. Process notation in DFD
Name application guidance processes:
- Name processes consisting of job and noun word that reflection that process function
- Never use word " processes "as part of name a bubble
- There are no several processes that have a same name
- Process shall numbered. Numbering of order possibility follow the flow or process of orders, however numbering order means not absolutely as process of order chronology.
DATA STORAGE
Data trove constitute trove of data who can as follows:
- A file or database at computer system
- An archives or manual note
- A data place box at someone table
- A manual referenced table
- An agenda or book
Data trove at DFD that in symbol can with a couple lining horizontal parallel that enclosed at one of its tip.
Picture4. Data Storage Symbol at DFD
1. A few things that needs to be noticed deep data trove depiction (source's data) : Just process just that in reference to data source, since one utilizes or revamp data at data source is a process.
2. Data flow that make towards data source of a process points out to process update to saved data at data source. Update can as added as or stored record or new document, deletion or takes document, and expurgation process.
3. Indigenous data flow of data source goes to a process point out that that process utilize data that is at data source.
4. To a process that does the two, which is utilizes and data source update can be chosen by use of one lining with dart two a purpose or utilizing two dart linings.
DFD SYMBOLS
DATA DICTIONARY
Data dictionary is a register organized element data with constant definition and according to system, so user and system analyst have same savvy about input, output, and data storage component. This data dictionary really to help the system analyst in define data that is flow in system, so definition is that data get compactly been done and most structure. Formation data dictionary is performed in analysis stage and design of a system.
On analysis stage, data dictionary constitute communication device among user and system analyst about data which is flow in system, which is about in going data to system and about information which needed by user. In the meantime, on lexical system scheme stage data is utilized to design input, reporting and database.
Formation data dictionary is gone upon path up data that exists on DFD. Groove data on DFD this gets global character, in mean just showing name grooves its data without showing structure of that data path. To showing structure of ala data path most inch therefore at forms data dictionary that is gone upon on data path in DFD.
Data dictionary load things as follows:
- Data flow name: shall on record that reader that require more explanation about a data flow can look for it squashy
- Alias: alias or other name of data gets to be written if available
- Data form: utilized to agglomerate data dictionary into its purpose one time of system scheme
- Data flow: showing of which data is flow and where data goes
- Explanation: giving explanation about meaning of data flow
BALANCING IN DFD
Data flow that turns in at and go out of one process have to equal data flow that turns in at and go out of details of process on level / level under it
- Data streaming name which turn in at and go out of one process have with by the name of data flow that turns in at and go out of details of that process
- Total and external entity of a process has to equal total and external entity of details of that process
- Things who shall be noticed on DFD who has more than one level:
- Shall available input balance and output among one level and next level
- 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
- Data streaming name, storage data and terminal on every level shall same if its object same
PROHIBITION IN DFD
1. Data flow may not from external entity directing to external entity another without via a process
2. Data flow may not of direct data storage make towards external entity without via a process
3. Data flow may not of direct data storage wend another data trove without via a process
4. Data flow of one process directing to wend another process without via an advisable data storage / one can maybe be avoided
References:
ER Ngurah Agus Sanjaya, S.KOM, M.KOM. Slide Part 4 - DATA FLOW DIAGRAM.
HM, Jogiyanto. 2005. Analisis & Desain Sistem Informasi. Yogyakarta: ANDI.
http://en.wikipedia.org/wiki/System_context_diagram
http://id.wikipedia.org/wiki/Data_flow_diagram
http://mugianet.com/attachments/012_Data%20Flow%20Diagram.pdf
No comments:
Post a Comment