Process ModelingProcess Modeling

FundamentalsFundamentals

Three Ways to Understand a SystemThree Ways to Understand a System

By its processesBy its processes What are the systems main processes?What are the systems main processes?

By its dataBy its data What data does the system maintain?What data does the system maintain?

By its outputBy its output What output will the system produce?What output will the system produce?

All 3 should be consistent with each other.All 3 should be consistent with each other.

When is Process Modeling done?When is Process Modeling done?

Process Modeling is part of the requirements Process Modeling is part of the requirements StructuringStructuring Stage. Stage.

We create process, logic and data models based on information gathered during We create process, logic and data models based on information gathered during the Requirements Determination stage (through interviews, surveys, etc.).the Requirements Determination stage (through interviews, surveys, etc.).

In this way, requirements structuring helps guide us through determination, e.g. In this way, requirements structuring helps guide us through determination, e.g. knowing what questions to ask in interviews.knowing what questions to ask in interviews.

Learning ObjectivesLearning Objectives

How to model organizational processes How to model organizational processes and the data they use, store and produceand the data they use, store and produce

Understand rules and guidelines for Understand rules and guidelines for drawing data flow diagrams drawing data flow diagrams

How to decompose data flow diagrams How to decompose data flow diagrams into lower-level diagramsinto lower-level diagrams

Rules of balancing data flow diagramsRules of balancing data flow diagrams

Learning ObjectivesLearning Objectives

Explain the differences among four types Explain the differences among four types of DFDs: current physical, current logical, of DFDs: current physical, current logical, new physical and new logicalnew physical and new logical

Discuss the use of data flow diagrams as Discuss the use of data flow diagrams as analysis toolsanalysis tools

What is Process Modeling?What is Process Modeling?

A way to graphically represent the system under A way to graphically represent the system under study as study as processes processes that capture, manipulate, that capture, manipulate, store and distribute data between a system and store and distribute data between a system and its environment and among system componentsits environment and among system components

There are many techniques that can be used for There are many techniques that can be used for modeling processesmodeling processes Structured analysis and design models processes Structured analysis and design models processes

with data flow diagrams (DFDs)with data flow diagrams (DFDs)Data flow diagrams are a way to graphically illustrate Data flow diagrams are a way to graphically illustrate movement of data between external entities outside the movement of data between external entities outside the system and the processes and data stores within a systemsystem and the processes and data stores within a system

Process ModelingProcess Modeling

Some deliverables and outcomes for Some deliverables and outcomes for current and proposed systemcurrent and proposed system Context data flow diagramContext data flow diagram Logical DFDs Logical DFDs

Level 0, level 1’s, etc.Level 0, level 1’s, etc.Technology independentTechnology independentShow data flows, structure and functional Show data flows, structure and functional requirements of systemrequirements of system

Processing logicProcessing logic Project dictionary and CASE repositoryProject dictionary and CASE repository

Four Types of Process ModelsFour Types of Process Models

CurrentCurrent ProposedProposed

LogicalLogical Physical aspects of system are removed Physical aspects of system are removed as much as possibleas much as possible

Current system is reduced to data and Current system is reduced to data and processes that transform themprocesses that transform them

Includes additional functionsIncludes additional functions

Obsolete functions are Obsolete functions are removedremoved

Inefficient data flows are Inefficient data flows are reorganizedreorganized

PhysicalPhysical Process label includes an identification Process label includes an identification of the technology (people or systems) of the technology (people or systems) used to process the dataused to process the data

Data flows and data stores are labeled Data flows and data stores are labeled with the actual name of the physical with the actual name of the physical media on which data flow or in which media on which data flow or in which data are storeddata are stored

Represents the physical Represents the physical implementation of the new implementation of the new systemsystem

Guidelines for Drawing DFDsGuidelines for Drawing DFDs

CompletenessCompleteness DFD must include all components necessary DFD must include all components necessary

for systemfor system Each component must be fully described in Each component must be fully described in

the project dictionary or CASE repositorythe project dictionary or CASE repository

ConsistencyConsistency The extent to which information contained on The extent to which information contained on

one level of a set of nested DFDs is also one level of a set of nested DFDs is also included on other levelsincluded on other levels

8.98.9

Guidelines for Drawing DFDsGuidelines for Drawing DFDs

TimingTiming Time is not represented well on DFDsTime is not represented well on DFDs Best to draw DFDs as if the system has never Best to draw DFDs as if the system has never

started and will never stop.started and will never stop.

Iterative DevelopmentIterative Development Analyst should expect to redraw diagram Analyst should expect to redraw diagram

several times before reaching the closest several times before reaching the closest approximation to the system being modeledapproximation to the system being modeled

8.108.10

Guidelines for Drawing DFDsGuidelines for Drawing DFDs

Primitive DFDsPrimitive DFDs Lowest logical level of decompositionLowest logical level of decomposition Decision has to be made when to stop Decision has to be made when to stop

decompositiondecomposition

8.118.11