DATA FLOW DIAGRAM
Data Flow Diagram
• Describing the system classification into a smaller modul
• Facilitate the user which less understand about computer to understand better about the systems under way
• Also called, a tools for making the systems model that allows the expert to describe the systems process as a functional network that connect as one with the data flow, either it is manually or computerized
Context Diagram
• Consist of one process and describe the scope of the system
• The highest level of DFD which describe all input into the system and output from the system
• System was limited by boundary (shown by ruptured line)
• Doesn't have a storage
• Steps for making context diagram :
- Specify the name of the system
- Determine the limits of the system
- Determine the terminator that exist in the system
- Determine what is to be received/given for the terminator from/to the system
- Draw the context diagram
Nil Diagram
• Describing the process from DFD
• Giving a comprehensive sight of view for the systems under way, to show the existing function or main process, data flow and external entity
• In this level there's possibility of data storage
• For process which didn't explained in detail for the next level, so it was added by simbol "*" or "P" in the end of the process number
• The balance of input and output (balancing) between nil diagram and context diagram must be well preserved
Detailed Diagram
• A diagram that explain which process should exist in the nil diagram or in the upper level
• Level numbering in DFD :
Level name Diagram 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, ...
• On one level, it should be better if there exist not more than 7 process and it should've max 9 process, if there're more than we must do the decomposition
Process Spesification
• Every process in the DFD must've a process spesification
• On the top level, the method that was used to figure the process can be in mean of descriptive sentence
• On more detail level, that was in the lowest level (functional primitive) need a more structured spesification
• Process spesification will be a guide for the programmer in making program (coding)
• The method that was used in process spesification : process explanation in the form of narrative, decision table, decision tree
External Unit
• Something that was exist outside of the system, but it gives data to the system or gives data from the system
• Simbolize by notation box
• External entity not included into the system
• Denomination :
- Terminal name used the any noun word
- Terminal mustn't have same name except the object is also the same
Data Flow
• Show the flow of the information
• Figured by a straight line that connecting component from the system
• Data flow shown by an arrow line given the name by the streaming data flow
• Data flow streams between yhe process, data storage and show the data flow from the data in form of the input for the system
• Guide for denomination :
- Naming for data flow consist of some word that connect to the connecting line
- There mustn't any data flow which has a same name and denomination must reflect the content
- Data flow consist of some element which denominated by element group
- Avoid using the word "data" and "information" for denomination in data flow
- The name of data flow must be written fully
• Another prescription :
- Data flow name which get into a process mustn't identic with the data flow name which come out from that system
- Data flow that get in or out from data storage may not given name if :
• The data flow is simple and easy to understand
• The data flow figures the entire of data item
- There mustn't any data flow from the terminal goes to the data storage or vice versa because terminal is not a part from the system, terminal relationship with data storage must go through the process
Process
• Process explained what should be done by the system
• Process may processed the data or incoming data flow into an outcoming data flow
• Process has a function to transformed one or more input data into one or more output data according to the desired spesification
• Every process has one or more input and produce one or more output
• Process also often called "bubble"
• Guide in process denomination :
- Process name consist of verb and noun which reflect the function of that process
- Never use a word "process" as a part of name for one bubble
- There mustn't any process which have a same name
- Process must given numbers. Number sequence considerably follows the flow or process sequence, but the number sequence doesn't mean the process sequence cronologically
Data Storage
• Data storage is a place to store tha data that exist in the system
• Simbolize by a parallel line or two line with one of the side spread wide open
• Process may take data from the database or give data to the database
• Guide for denomination :
- The name must reflect data storage
- If the name consist of more than one word so we must give a conjunction sign
DFD Symbol
Data Dictionary
• Has a function to help the systems subject to interpret the application in detail and organize all data element that was used by the system exactly so that the user and system analyst have a same basic understanding about the input, output, storage, and process
• In analyzing phase, the data dictionary was used to communicate between system analyst and the user
• In system development phase, the data dictionary was used to develop the input, report, and database
• Data flow in DAD has a global characteristic, more detail explanation can be seen in data dictionary
• Data dictionary contains all these things :
- Data flow name must be taken note in order for the reader who needs detailed explanation about one data flow can search through it more easily
- Alias or other name for the data must be written if exist
- Data shape was used in categorizing data dictionary into its usage when developing systems
- Data flow shows from where the data flows and where the data headed
- Explanation, give the explanation about the meaning of the data flow
Balancing in DFD
• Data flow that goes in and out from one process must be equal with the data flow that goes in and out from the detailed process in the under level
• Data flow name that goes in and out from one process must be equal with the name of data flow that goes in and out from that detailed process
• The number and name from external entity from one process must be equal with the number and name of the external entity from that detailed process
• Things that should be taken note for in DFD that has more than one level :
- There must be a balance in input and output between one level and other level
- Balance between level 0 and level 1 can be seen in input/output from the data flow to/from the terminal in level 0, while the balance in level 1 and level 2 can be seen in input/output from data flow to/from the relevant process.
- Data flow name, data storage and terminal in every level must be equal if the object is also the same
Prohibition In DFD
• Data flow mustn't be from external entity directly go to other external entity without going through some process
• Data flow mustn't be from data storage directly go to external entity without going through some process
• Data flow mustn't be from data storage directly go to other data storage without going through some process
• Data flow from one process directly go to other process without going through some data storage should likely be avoided
Data Flow Diagram
• Describing the system classification into a smaller modul
• Facilitate the user which less understand about computer to understand better about the systems under way
• Also called, a tools for making the systems model that allows the expert to describe the systems process as a functional network that connect as one with the data flow, either it is manually or computerized
Context Diagram
• Consist of one process and describe the scope of the system
• The highest level of DFD which describe all input into the system and output from the system
• System was limited by boundary (shown by ruptured line)
• Doesn't have a storage
• Steps for making context diagram :
- Specify the name of the system
- Determine the limits of the system
- Determine the terminator that exist in the system
- Determine what is to be received/given for the terminator from/to the system
- Draw the context diagram
Nil Diagram
• Describing the process from DFD
• Giving a comprehensive sight of view for the systems under way, to show the existing function or main process, data flow and external entity
• In this level there's possibility of data storage
• For process which didn't explained in detail for the next level, so it was added by simbol "*" or "P" in the end of the process number
• The balance of input and output (balancing) between nil diagram and context diagram must be well preserved
Detailed Diagram
• A diagram that explain which process should exist in the nil diagram or in the upper level
• Level numbering in DFD :
Level name Diagram 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, ...
• On one level, it should be better if there exist not more than 7 process and it should've max 9 process, if there're more than we must do the decomposition
Process Spesification
• Every process in the DFD must've a process spesification
• On the top level, the method that was used to figure the process can be in mean of descriptive sentence
• On more detail level, that was in the lowest level (functional primitive) need a more structured spesification
• Process spesification will be a guide for the programmer in making program (coding)
• The method that was used in process spesification : process explanation in the form of narrative, decision table, decision tree
External Unit
• Something that was exist outside of the system, but it gives data to the system or gives data from the system
• Simbolize by notation box
• External entity not included into the system
• Denomination :
- Terminal name used the any noun word
- Terminal mustn't have same name except the object is also the same
Data Flow
• Show the flow of the information
• Figured by a straight line that connecting component from the system
• Data flow shown by an arrow line given the name by the streaming data flow
• Data flow streams between yhe process, data storage and show the data flow from the data in form of the input for the system
• Guide for denomination :
- Naming for data flow consist of some word that connect to the connecting line
- There mustn't any data flow which has a same name and denomination must reflect the content
- Data flow consist of some element which denominated by element group
- Avoid using the word "data" and "information" for denomination in data flow
- The name of data flow must be written fully
• Another prescription :
- Data flow name which get into a process mustn't identic with the data flow name which come out from that system
- Data flow that get in or out from data storage may not given name if :
• The data flow is simple and easy to understand
• The data flow figures the entire of data item
- There mustn't any data flow from the terminal goes to the data storage or vice versa because terminal is not a part from the system, terminal relationship with data storage must go through the process
Process
• Process explained what should be done by the system
• Process may processed the data or incoming data flow into an outcoming data flow
• Process has a function to transformed one or more input data into one or more output data according to the desired spesification
• Every process has one or more input and produce one or more output
• Process also often called "bubble"
• Guide in process denomination :
- Process name consist of verb and noun which reflect the function of that process
- Never use a word "process" as a part of name for one bubble
- There mustn't any process which have a same name
- Process must given numbers. Number sequence considerably follows the flow or process sequence, but the number sequence doesn't mean the process sequence cronologically
Data Storage
• Data storage is a place to store tha data that exist in the system
• Simbolize by a parallel line or two line with one of the side spread wide open
• Process may take data from the database or give data to the database
• Guide for denomination :
- The name must reflect data storage
- If the name consist of more than one word so we must give a conjunction sign
DFD Symbol
Data Dictionary
• Has a function to help the systems subject to interpret the application in detail and organize all data element that was used by the system exactly so that the user and system analyst have a same basic understanding about the input, output, storage, and process
• In analyzing phase, the data dictionary was used to communicate between system analyst and the user
• In system development phase, the data dictionary was used to develop the input, report, and database
• Data flow in DAD has a global characteristic, more detail explanation can be seen in data dictionary
• Data dictionary contains all these things :
- Data flow name must be taken note in order for the reader who needs detailed explanation about one data flow can search through it more easily
- Alias or other name for the data must be written if exist
- Data shape was used in categorizing data dictionary into its usage when developing systems
- Data flow shows from where the data flows and where the data headed
- Explanation, give the explanation about the meaning of the data flow
Balancing in DFD
• Data flow that goes in and out from one process must be equal with the data flow that goes in and out from the detailed process in the under level
• Data flow name that goes in and out from one process must be equal with the name of data flow that goes in and out from that detailed process
• The number and name from external entity from one process must be equal with the number and name of the external entity from that detailed process
• Things that should be taken note for in DFD that has more than one level :
- There must be a balance in input and output between one level and other level
- Balance between level 0 and level 1 can be seen in input/output from the data flow to/from the terminal in level 0, while the balance in level 1 and level 2 can be seen in input/output from data flow to/from the relevant process.
- Data flow name, data storage and terminal in every level must be equal if the object is also the same
Prohibition In DFD
• Data flow mustn't be from external entity directly go to other external entity without going through some process
• Data flow mustn't be from data storage directly go to external entity without going through some process
• Data flow mustn't be from data storage directly go to other data storage without going through some process
• Data flow from one process directly go to other process without going through some data storage should likely be avoided
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