Data Flow is a network diagram illustrating a computerized system, manual or a combination of both, and representation in the form of a set of structured system components that are interconnected in accordance with the rules play. Advantage of DFD is possible to describe the system from the most high level and then them into a lower level (decomposition), whereas the lack of the DFD does not indicate the process is looping, decision-making process and the process of calculation.
Data Flow Diagram Symbols
- External Entity
- Data Flow
- Data Store
This symbol is used to describe the origin and destination data. External Entity can be a person, group of people, organizations, departments in the organization, or the same company, but in system beyond the current model is made. External Entity may also include departments, divisions or outside the systems that communicate with the system that is currently being developed.
This symbol is used to describe the flow of data that are running. Data flow direction is indicated with arrows and lines give the name on the flow of data flow. Data flow between the process flow, data storage and data flow indicates that the form of data input to the system.
Guidelines of the name: (1) Name of the data flow that consists of some words associated with the flow line speed. (2) Name of the data flow that consists of some words associated with the flow line speed. (3) Data flow that consists of several elements can be expressed with the group elements. (4) Avoid using the word ‘data’ and ‘information’ to give a name to the data flow. (5) The extent possible the complete data flow is written.
Terms of others in making the symbols are: (1) Name of the data flow into a process may not be the same as the name of the data flow out of the process. (2) There can be no data flow 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 the process. (3) Data flow into or out of data storage does not need to be given a name if: a) Data flow simple and easily understood. b) Data flow describing the entire data item.
This symbol is also called the bubble, used for processing or data transformation. Guidelines of the process: (1) Name of the process consists of a verb and noun, which reflects the function of the process. (2) Do not use the process as part of the name of a bubble. (3) There may be some process that has the same name. (4) The process must be given a number. Order number wherever possible to follow the flow of the process or sequence, but the sequence number does not mean that the absolute is a process in chronological order. There are four possibilities that can occur in the process in relation with the input and output:
This symbol is used to describe the data flow is saved or archived. Data store is usually associated with the storages, such as file or database associated with the storage computerization, such as a diskette file, files, hard disk, magnetic tape files. Data store is also related to the storage manually, such as books address, file folder, and agenda. A data store associated with the data flow only on the components process, not with the other components DFD.
Stages Data Flow Diagram
- Context Diagram
- Zero Diagram
- Detailed Diagram
This diagram is created to describe the source and destination data will be processed or in other words the diagram is used to describe the system in general / global system of the entire existing. In this diagram there is no storage. Consists of a process and describe the scope of a system. Consists of a process and describe the scope of a system.
This diagram is created to describe the stages of the process in the context diagram, a more detailed penjabarannya. On this system there may be data storage.
This diagram is created to describe the data flow in more play more phases of the process in the diagram is zero. In a level should be, there are only 7 to 9 process. Numbering level in the DFD:
Data Dictionary (DD)
- Data flow
- Name of Data Flow
- Type of Data
- Data Structure
Data flow from which the data shows the flow and where the data will go. Description of data flow should be noted in this data dictionary to make it easier to find in the data flow data flow diagram (DFD).
Because the data dictionary is based on a data flow that flows in the data flow diagram, the flow of data should also be noted in the data dictionary, so that those who read the DFD and requires further explanation about a particular data flow data flow diagram can browse easily in the data dictionary.
Data flow can flow from the flow of a process to other processes. Data which is usually in the form of reports and documents of printing machines. Thus the shape of the data flow can be a basic document or form, the computer prints the document, the report is printed, the display screen on the monitor, variables, parameters and field-field. Forms of data such as this should be noted in the data dictionary.
Shows the data structure of data flow is recorded in the data dictionary that consists of items or elements of the data.
Alias or the name of the data must also be written. Alias is needed because the data have the same name that is different to other people or departments.
Volume that needs to be noted in the data dictionary is the volume average and peak volume of data flow. Volume shows the average number of data flow that flows in one period certain volume while the volume of the peak indicates the most.
This period indicates when the occurrence of data flow. Period should be noted in the data because the campus can be used to identify when the input data must be entered into the system, when the program should be done and when reports should be produced.
To further clarify the meaning of the data flow is recorded in the data dictionary, then the explanation can be charged with the particulars of the data flow.