DATA FLOW DIAGRAM

DATA FLOW DIAGRAM
Data Flow Diagram (DFD) is a means of making the model system allows the professional to describe the system process as a functional network that is connected to one with flow data, either manually or computerized. DFD is a tool of making a model that provides emphasis only on the function of the system. DFD is a tool that system design-oriented flow data with the concept of decomposition can be used to depiction and analysis of system design that is easily
communicated by professionals and users to the system the program.
Also called Data Flow Diagram (DFD) to describe the system modules in a smaller, easier and less understanding of the field to understand the computer system that will be done.

Diagram context
• include one process and expressed scope from a system
• it's the highest level from DFD which expressed all input into the system and output from system
• System is bounded by the boundary (it's shown by the dashed line)
• there isn't any storage

This diagram is the highest-level diagram of the DFD describes the relationship with the environment outside the system.
1. Specify the name of the system.
2. Determine the limits of the system.
3. Determine the terminator are present in the system.
4. Determine what is received / given terminator from / to the system.
5. Drawing context diagram.

Zero diagram
1. Describes process of DFD.
2. Providing views on the overall system in which, showing the main function or process that is, the flow of data and entity external
3. At this level of data storage possible
4. To process that does not detailed again on the next level then added to the symbol '*' or 'P' at the end of the process
5. Balance of input and output (balancing) between 0 to diagram context diagram should be maintained

Detailed Diagram
Detailed Diagram is diagrams that decompose a process that is in the diagram zero level or above
Numbering level in the DFD.
In 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 specification process
At the top level method is used to describe the process can use a sentence with descriptive
At a more detailed level, namely on the bottom (functional primitive) requires specification of a more structured
Specification process will be the guideline for the programmer to make this program (coding)
Method used in the specification process: the process of disintegration in the form of a story, decision table, decision tree.

ON FOREIGN
1. Something that is outside the system, but it provides data in the system or to provide data from the system
2. Symbol with the notation
3. External entity not part of the system including
4. Naming:
• The name of the form of noun
• Terminal may not have the same name except the same object
Sure every system has a limit system (Boundary) that a separate system with the outside environment. System will receive input and produce output to the outside environment. Unity outside (external entity) is the unit (entity) in environment outside the system that can be a person, organization or other system that is located outside in environment that will provide input or receive output from the system.

DATA FLOW
• Is the place flow information
• Depicted with the 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 that flows
• Flow data flow between processes, data storage and data flow indicates that the form of data input for the system
Data flow in DFD is given an arrow symbol. This data flow between processes, store data, and external entity. This data flow represents the flow of data can be input to the system or the results of the processing system.
1. Packet of data
When two or more of a source to the same destination the same, it should be considered as a single stream of data, because two or more data flows together as a package. The data flow must be indicated as with the data flow, even though for example consist of several documents.
2. Diverging data flow
Data flow that spreads shows a number of copies of the same data flow from the same source to different purposes.
3. Converging data flow
Gather flow data showed that some of the data flow that is different from different sources to join with the same goal.
4. Cracked the concept and purpose of data flow
All data flow must be generated from a process (can be one or both, that is derived from a process or not come from a process but a process leading to or coming from a process and to a process). Concept is important because the flow of data is one of the results of a process or will be used to perform a process.

Processes
• The process is what is done by the system
• The process can process data flows or data entry into the flow of data out
• 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
• Each process has one or more inputs and produce one or more output
• The process also often called bubble

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 does not mean that the absolute is a process in chronological order

A process is an activity or work done by the people, machines, or the results of a computer data that flow into the process to produce data that will flow out of the process. for physical data flow diagrams (PDFD), the process can be done by people, machinery, computers and for logical data flow diagram (LDFD), a process only shows the process from the computer.
a. Identification data
This identification included of a number that shows the reference number of the process.
b. Process name
the name of the process shows what is done by the process.
c. Processing
PDFD to indicate that the process is not only the process of the computer but also a manual process, such as the process is done by people, machinery, and so forth. This shows the processor who or where the process is done. LDFD, here for as a processor is program that the process referred.

DFD error location is:
• Process does not have any input but the output, this error is called black holes, because the data into the process and the like disappeared into a black hole.
• The input process but did not receive the input, the error is called the miracle.

Data storage
a. Data storage is a storage place for data that exists in the system
b. Symbol with a pair of parallel lines or two lines with one side open side
c. The process can retrieve data from or provide data to the database
d. Guidelines of the name:
• The name should reflect the data storage
• When his name more than one word must be marked with the number


Data dictionary
Work to help the system to interpret the application in detail and organize all elements of the data used in the system precisely so that the system analyst and have a basic understanding of the same input, output, storage and process. 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. Flow data on the global DAD, further details can be seen in the data dictionary.


Contain of Data dictionary
1. Name of data flow: must note that readers who need further explanation about a flow of data can find it easily.
2. Alias: alias 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.
6. Period: at the occurrence of the data showed, that the DD can know when the input is input to the system, when the program is done, and when the report produced.
7. Volume: the volume should be noted is the volume average (the average number of flow data that flows in a certain period) and the peak volume (highest volume). Volume is how much to use external storage to be used.
8. Structure data: shows the flow of data recorded in the DD of the items whatever.

Balancing IN DFD
a. 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 / levels below.
b. Name of the data flow into and out of the process must match the name of the flow of data into and out of the details of the process.
c. 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.
d. The issues that must be considered in the DFD which have more than one level:
• There must be a balance between input and output of one level and next level.
• Balance between level 0 and level 1 at the input / output of stream 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 / from the process concerned.
• Name of the flow of data, data storage and terminals at each level must be the same if the same object.

Restrictions in DFD
a) Flow data may not be from outside the entity directly to other outside entities without going through a process.
b) Flow data may not be from the savings directly to the data to outside entities without going through a process.
c) Flow data may not be saving the data directly from the savings and other data without going through a process.
d) Flow data from one process directly to the other without going through the process of saving data should / be avoided as much as possible