Data flow Diagram

DATA FLOW DIAGRAM
Data Flow Diagram (DFD) is a diagram using the notation-notation to describe the flow of data from the system, which is very helpful to understand the logic of the system, and tersruktur clear.
CONTEXT DIAGRAM
Context diagram of a process and describe the scope of a system and is the highest level of the DFD that describes the entire input to the system and output of the system.
ZERO DIAGRAM
Zero diagram is a chart that describes the process of DFD. This diagram provides a view of the overall system shows that the main function of the process or the flow of data and the external entity. At this level there is a data storage.
DETAILED DIAGRAM
Is a diagram that decipher what is the process in the diagram zero level or above. one level there should be no more than 7 units and the maximum of 9, when more should be done in the decomposition.
SPECIFICATION PROCESS
Each process in the DFD must have a top-level specification process . method that is used to describe the process can use a sentence with descriptive, and on a more detailed level, namely on the bottom (functional primitive) require a more structured specification, process specification will be the guidelines for a programmer to create the program.
EXTERNAL ENTITY
Unit outside is something that is outside the system, but provide data in the system or to provide data from an external system. Entity not including part of the system, the symbols with the notation.
DATA FLOW
Data flow is the information flow is depicted with a straight line that connects the components of the system. Data flow direction is indicated with arrows and lines give the name on the flow of data flow. Flow data that flows between processes, data storage and data flow indicates that the form of data input to 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
Other provisions:
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 doesn’t need to be given a name if:
a. The flow of data simple and easy to understand
b. Describes the data flow of all 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
PROCESS
The process is what is done by the system, can process data streams or input data into output data stream. Each process has one or more inputs and produce one or more output.
Transform the process of working one or more of the input data into one or more of the output data in accordance with the desired specifications.
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. May not have some process that has the same name
4. The process should be given a number. Order number wherever possible to follow the flow of the process or sequence, but the sequence number doesn’t mean that the absolute is a process in chronological order
DATA STORAGE
Data storage is a storage place for data that exists in the system, which symbol with a pair of parallel lines or two lines with one of the side open. The process can retrieve data from or provide data to the database.
Guidelines of the name:
1. The name should reflect the data.
2. When his name more than one word must be marked with the numbers.
DATA DICTIONARY
Data Dictionary functions to help the system to interpret the application in detail and manage all elements of the data used in the system right so that the system analyst and have a basic understanding of the same input, output, storage and processing.
At analysis, the data dictionary is used as a means of communication between the systems analyst with the user. At the system design, data dictionary is used to design input, reports and databases.
Data dictionary contains the following:
1. Name of data flow: must note that readers who need further explanation about a flow of data can find it easily
2. Alias: initials or other name of the data can be written when there is
3. Forms of data: used to segment the data dictionary to use when designing the system
4. Flow data: indicates from which data flows and where the data
5. Description: to give an explanation of the meaning of the data flow
BALANCING IN DFD
The flow of data into and out of a process must be the same as the flow of data into and out of the details of the process on the level or levels below it. Number and the name of an entity outside the process must be equal to the number of names and entities outside of the details of the process.
The issues that must be considered in the DFD which have more than one level:
1. There must be a balance between input and output of one level and next level
2. Balance between level 0 and level 1 at input output of the flow of data to or from the terminal on level 0, while the balance between level 1 and level 2 is seen on the input / output of stream data to and from the process concerned
3. Name of the flow of data, data storage and terminals at each level must be the same if the same object
RESTRICTIONS IN DFD
1. Flow data may not be from outside the entity directly to other outside entities without going through a process
2. Flow data may not be from the savings directly to the data to outside entities without going through a process
3. Flow data may not be saving the data directly from the savings and other data without going through a process
4. Flow data from one process directly to the other without going through the process of saving data should be avoided as much as possible