Context Diagram
> consist of a process and describing scope from a system
> the highest level from DFD that describing all input to system and output from system.
> system limited by boundary (that described with dash line)
> there is not be able to storage.
Zero Diagram
> describing process of DFD
> giving opinion totally about handled system, indicate function or main process that exist, data flow and external entity.
> in this level, enable for data storage.
> for unexplained process in next level ,then addicted symbol ‘*’ or ‘P’ in last number of process.
> balancing input and output between Zero diagram and context diagram must protected.
Detail Diagram
> the diagram that explaining what process inside zero diagram or next up level.
> number sequence level of DFD
> inside a level better not have more than 7 process and maximal 9, if more then must do decomposition.
Process Specification
> every process in DFD must have process specification
> in top level method that used for describing process with descriptive sentence
> in detail level that is in bottom process (functional primitive) requiring specification more structured.
> process specification can be guide for programmer in coding
> method that used in process specification: explain process in narrative, decision table, decision tree.
External Unity
> Something outside system, but its giving data into system or giving data from system
> symbol by box notation
> external entity not included as part as system
> giving name :
==> terminal name in the form of noun
==>terminal cannot have the same name, except the same object
Data Flow
> representing place stream of information
> described with straight line that connecting component from system
> data flow shown with arrow and line that given name as stream data flow
> data flow stream among process, data storage and showing data flow from data as input for system
> guidance of giving name :
==> name of data flow consist of some word stream connected with continue line
==> there is can’t be data flow that have same name and giving name must expressing its.
==> data flow consist of some element can be expressed with element group
==> avoid usage of word ‘data’ and ‘information’ for giving a name in data flow
==> as possible, the name of data flow fully written
> another rules :
==> the name of data flow enter into a process cannot same with the name of data flow that out from that process
==> data flow that in or out from data storage haven’t to given name if :
====> simple data flow and easier to understand
====> data flow describing all data item
==> there are can’t be data flow from terminal to data storage or on the contrary because terminal is not part of system, connection between terminal and data storage must pass process
Process
> process represented what system done
> process can turn data or input data flow into output data flow
> process functioning for transformation one or some input data become one or more output data appropriate with specification needed
> every process have one or some input and resulting one or some output
> process as known as bubble
> guidance of giving name process :
==> name process consist of verb and noun that expressing its function process
==> don’t using process word as part name a bubble
==> there is can’t be some process have the same name
==> process must given number. Number sequence as possible follow stream or process sequence. However number sequence can’t absolutely represented process sequence chronologically.
Data Storage
> represented existing data repository in system
> symbol with a couple of parallel line or two line with one of other side was open.
> process can taking data from or giving data to database
> guidance of giving name :
==> name must expressing data storage
==> if its name more that one word then must given continued sign
Symbol DFD
Data Dictionary
> function as helping system performer for interpreting application in detail and organizing all data element that used system precisely until user and system analyst having same basic knowledge about input, output, storage and process
> in analysis stage, data dictionary used as communication tools between system analyst and user
> in system planning stage, data dictionary used for make an input, report and database
> Data flow in DAD having global character, for more information can seen in data dictionary
> data dictionary loading the followings :
==> name of data flow: have to recorded in order to reader that needing more clarification about a data flow can easy to search
==> data form : used for grouping data dictionary into usage when system planning
==> data flow : showing where data streaming from and go.
==> clarification : giving explain about the meaning from data flow
Balancing inside DFD
> data flow that in into and out from one process must same with data flow that in into and out from process detailed in bottom level/standard
> the name of data flow that in into and out from one process must same with data flow that in into and out from process detailed
> amount and external entity name from a process must same with amount and external entity name from its process detailed
> things which must have to attention in DFD owning more than one level :
==> there is balancing input and output between one level and next level
==> balancing between level 0 and level 1 seen in input/output from data flow to or from terminal in level 0, while balancing between level 1 and level 2 seen in input/output from data flow to or from its process
==> name of data flow, data storage and terminal in each level must same if have same object
Prohibition inside DFD
> data flow mustn’t from external entity direct to other external entity without pass a process
> data flow mustn’t from data storage direct to external entity without pass a process
> data flow mustn’t from data storage direct to other data storage without pass a process
> data flow from one process direct to other process without pass a data storage better to / as possible avoided
reference:
> Slide PPT : Part 4 -DATA FLOW DIAGRAM, oleh : NGURAH AGUS SANJAYA ER, S.KOM, M.KOM
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