20-05-2013, 03:56 PM
Process Modeling
Process Modeling.ppt (Size: 1.43 MB / Downloads: 22)
Key Definitions
A process model is a formal way of representing how a business operates
Data flow diagramming shows business processes and the data that flows between them
Logical process models describe processes without suggesting how they are conducted
Physical models include information about how the processes are implemented
Context Diagram
Shows the context into which the business process fits
Shows the overall business process as just one process
Shows all the outside entities that receive information from or contribute information to the system
Level 0 Diagram
Shows all the processes that comprise the overall system
Shows how information moves from and to each process
Adds data stores
Level 1 Diagrams
Shows all the processes that comprise a single process on the level 0 diagram
Shows how information moves from and to each of these processes
Shows in more detail the content of higher level process
Level 1 diagrams may not be needed for all level 0 processes
Level 2 Diagrams
Shows all processes that comprise a single process on the level 1 diagram
Shows how information moves from and to each of these processes
Level 2 diagrams may not be needed for all level 1 processes
Correctly numbering each process helps the user understand where the process fits into the overall system
Data Flow Splits and Joins
A data flow split shows where a flow is broken into its component parts for use in separate processes
Data flow splits need not be mutually exclusive nor use all the data from the parent flow
As we move to lower levels we become more precise about the data flows
A data flow join shows where components are merged to describe a more comprehensive flow
Alternative Data Flows
Where a process can produce different data given different conditions
We show both data flows and use the process description to explain why they are alternatives
Tip -- alternative data flows often accompany processes with IF statements
DFD Fragment Tips
All process names must be verb phrases
Maintain organization’s viewpoint in naming processes
Layouts often place
processes in the center
inputs from the left
outputs to the right
stores beneath the processes
Validating the DFD
Syntax errors
Assure correct DFD structure
Semantics errors
Assure accuracy of DFD relative to actual/desired business processes
User walkthroughs
Role-play processes
Examine lowest level DFDs
Examine names carefully
Summary
The Data Flow Diagram (DFD) is an essential tool for creating formal descriptions of business processes and data flows.
Use cases record the input, transformation, and output of business processes.
Eliciting scenario descriptions and modeling business processes are critically important skills for the systems analyst to master.