IS 460 Notes Documenting a System Analysis with Dataflow Diagrams By Thomas Hilton

System Analysis The foundation skill of IS Professionals The foundation skill of IS Professionals Understanding Whole Systems via the Systems View Understanding Whole Systems via the Systems View Outputs Outputs Information Information Other Other Inputs Inputs Data Data Other Other Processes Processes Hardware Hardware Software Software People People Procedures Procedures User Perspective! User Perspective!

Systems are Complex They Can Only be Understood by “Functional Decomposition” They Can Only be Understood by “Functional Decomposition” Invoke the System-Supersystem- Subsystem view Invoke the System-Supersystem- Subsystem view Alternate between the Black Box Concept and the Closed System Concept Alternate between the Black Box Concept and the Closed System Concept Create Successive Levels of Detail Create Successive Levels of Detail

Information Systems Components Entities External to the System Entities External to the System “Data” that Flows Through the System “Data” that Flows Through the System Processes that Receive and Produce Data Processes that Receive and Produce Data “Data Stores” that store data “Data Stores” that store data

Information Systems Components External Entity External Entity Dataflow Dataflow Process Process Datastore Datastore Process name x.x Data Store NameDx Entity Name Data Flow Name

Levels of Detail Context Level Context Level Level 0 Level 0 Levels 1, 2, etc. Levels 1, 2, etc. Functional Primitive Level Functional Primitive Level

Processes Explode Each process at a higher level corresponds to a set of processes at the next lower level Each process at a higher level corresponds to a set of processes at the next lower level x.x Entity Name x.x

Some Traits of the Example Every dataflow starts somewhere and ends somewhere Every dataflow starts somewhere and ends somewhere Dataflows at a lower level agree with the dataflows of their parent process Dataflows at a lower level agree with the dataflows of their parent process No dataflow exits and enters the same process No dataflow exits and enters the same process Every process has at least one input and at least one output Every process has at least one input and at least one output Every process explodes to at least two subprocesses Every process explodes to at least two subprocesses Some processes don’t explode; these are called functional primitives, and they contain pseudocode Some processes don’t explode; these are called functional primitives, and they contain pseudocode

Pseudocode, the Right Idea… Pseudo = fake, false Pseudo = fake, false Code = software instructions Code = software instructions Select NAME, ADDRESS From TABLE Where CREDIT_LIMIT.GE Fake variable names Fake table name Fake conditions Incorrect syntax

Questions? On to an Example! On to an Example!