By Orvilla V. Balangue, MSCS

SAS-ICT Faculty

Learning ObjectivesDifferentiate logical and physical system models.Define process modeling and explain its benefits.Recognize and understand the basic concepts

and constructs of a process model.Read and interpret a data flow diagram.Construct a context diagram to illustrate a

system interfaces with its environment.Perform even partitioning and organize events

in a functional decomposition diagram.Draw event diagrams and merge those event

diagrams into system diagrams.Document the distribution of processes to

locations.

Topic OutlineV. SYSTEM ANALYSIS METHODS-PROCESS

MODELING

System Modeling

Logical Process Modeling

Process Models

System modellingSystem modelling helps the analyst to

understand the functionality of the system and models are used to communicate with customers.

Different models present the system from different perspectivesExternal perspective showing the system’s

context or environment;Behavioural perspective showing the behaviour

of the system;Structural perspective showing the system or

data architecture.

Model TypesData processing model showing how the

data is processed at different stages.Composition model showing how entities

are composed of other entities.Architectural model showing principal

sub-systems.Classification model showing how entities

have common characteristics.Stimulus/response model showing the

system’s reaction to events.

V. SYSTEM ANALYSIS METHODS-PROCESS MODELING

System Modeling

Logical Process Modeling

Process Models

Logical Process ModelA logical level process model is used to model

the detailed requirements of an application system. During analysis, the conceptual process model evolves into the detailed functional requirements, or logical process model.

It describes the behaviour of processes and their interactions.

Process modelling at the logical level builds a detailed process model used to describe the functional requirements of an application system from which a physical design can be derived.

(Padernal, 2013) Flood Monitoring and Warning System

(Hinojales, 2014) Mobile Commerce for Nerp’s RIG Enterprise

Document Flow DiagramsA document flow diagram is a

graphical image that is used to provide a clear representation of a business function.

It is a technique that begins with an overall picture of the business and then proceeds to analyze each of the functional zones of interest.

What is a Workflow Diagram?Workflow diagram usually denotes

movement of documents, resources, and data throughout the entire work process for a specific product or service.

Work processes can be very complicated, so visual representation of how the task should be completed can help employees better understand the process and work more efficiently.

Workflow DiagramWorkflow diagrams show persons responsible for every sub-process, necessary documents, resources, data and amount of time requires at each stage.

Why use Workflow diagrams?Workflow diagram is important to understand the complete work process as it helps you to:

- Understand your own responsibilities;

- Understand role of other employees; - Analyze the entire process and define problem areas and bottlenecks;

Why use Workflow diagrams?Identify critical stages;Improve communication as diagram shows relationships between different stages in a process;

Explore the complete list of required documents and resources.

Context modelsContext models are used to illustrate the

operational context of a system - they show what lies outside the system boundaries.

Social and organisational concerns may affect the decision on where to position system boundaries.

Architectural models show the system and its relationship with other systems.

The context of an ATM system

Auto-tellersystem

Securitysystem

Maintenancesystem

Accountdatabase

Usagedatabase

Branchaccounting

system

Branchcountersystem

Process modelsProcess models show the overall process and

the processes that are supported by the system.

Data flow models may be used to show the processes and the flow of information from one process to another.

Equipment procurement process

Get costestimates

Acceptdelivery ofequipment

Checkdelivered

items

Validatespecification

Specifyequipmentrequired

Choosesupplier

Placeequipment

order

Installequipment

Findsuppliers

Supplierdatabase

Acceptdelivered

equipment

Equipmentdatabase

Equipmentspec.

Checkedspec.

Deliverynote

Deliverynote

Ordernotification

Installationinstructions

Installationacceptance

Equipmentdetails

Checked andsigned order form

Orderdetails plusblank order

form

Spec. +supplier +estimate

Supplier listEquipment

spec.

Data-processing modelsData flow diagrams (DFDs) may be used to

model the system’s data processing.These show the processing steps as data

flows through a system.DFDs are an intrinsic part of many analysis

methods.Simple and intuitive notation that customers

can understand.Show end-to-end processing of data.

What are Data Flow Diagrams? A data flow diagram (DFD) is a graphical

representation of the "flow" of data through an information system.

A data flow diagram can also be used for the visualization of data processing (structured design).

It is common practice for a designer to draw a context-level DFD first which shows the interaction between the system and outside entities.

This context-level DFD is then "exploded" to show more detail of the system being modeled

Advantage of DFDHelps to understand the technical

implementation of the system too early

Helps to understand the interrelationships of systems and subsystems

Helps in communicating current system knowledge to users

Helps to analyze the system

Four Basic Symbols

External EntitiesRepresent people or organizations outside of

the system being studiedShows the initial source and final recipient of

data and informationShould be named with a noun, describing

that entity

Customer

External EntitiesExternal entities may be

A person, such as CUSTOMER or STUDENTA company or organization, such as BANK

or SUPPLIERAnother department within the company,

such as ORDER FULFILLMENTAnother system or subsystem, such as the

INVENTORY CONTROL SYSTEM

ProcessesRepresent either:

A whole systemA subsystemWork being done, an activity

Names should be in the form verb-adjective-nounThe exception is a process that represents

an entire system or subsystem

1

Add NewCustomer

2Customer

InquirySubsystem

Data StoresName with a noun, describing the data Data stores are usually given a unique

reference number, such as D1, D2, D3 Include any data stored, such as:

A computer file or databaseA transaction file A set of tables A manual file of records

D1 CustomerMaster

Data Flow

Shows the data about a person, place, or thing that moves through the system

Names should be a noun that describes the data moving through the system

Arrowhead indicates the flow directionUse double headed-arrows only when a

process is reading data and updating the data on the same table or file

Customer RecordNew Customer

Guidelines for Developing DFD

Create the context level diagram, including all external entities and the major data flow to or from them

Create Diagram 0 by analyzing the major activities within the context process Include the external entities and major data

storesCreate a child diagram for each complex

process on Diagram 0

Creating Data Flow DiagramsMaking a list of business activitiesAnalyzing what happens to an input data

flow from an external entityAnalyzing what is necessary to create an

output data flow to an external entityExamining the data flow to or from a data

storeAnalyzing a well-defined process for data

requirements and the nature of the information produced

Unclear areas of a data flow diagram should be noted and investigated

Context Level DFDContains only one process, representing

the entire systemThe process is given the number zeroAll external entities are shown on the

context diagram as well as major data flow to and from them

The diagram does not contain any data stores

Context Level DFD (Example)

Diagram 0Diagram 0 is the explosion of the context level

diagramShould include up to 7 or 9 processes

Any more will result in a disorganized diagramProcesses are numbered with an integerThe major data stores and all external entities are

included on Diagram 0

Diagram 0 (Example)

Child Diagrams (Levels 1, 2, 3, …)Each process on diagram zero may be

exploded to create a child diagramEach process on a lower-level

diagram may be exploded to create another child diagram

The processes on the child diagram are numbered using the parent process number, a decimal point

Child Diagrams

Examples are:Process 3.2 is the child of process 3Process 5.2.7 is the child of process 5.2

3.2

EditCustomer

5.2.7

CalculateCustomerDiscount

Child DiagramsExternal entities are usually not shown on

the child diagrams below Diagram 0If the parent process has data flow

connecting to a data store, the child diagram may include the data store as well

Child Diagrams (Example)

Child DiagramsA lower-level diagram may contain data

stores not shown on the parent process, such asA file containing a table of information (such

as a tax table)A file linking two processes on the child

diagramMinor data flow, such as an error line, may

be included on a child diagram

DFD Rules Each process must have a minimum of one data flow going into it

and one data flow leaving it.

Each data store must have at least one data flow going into it and

one data flow leaving it.

A data flow out of a process should have some relevance to one or

more of the data flows into a process.

Data stored in a system must go through a process.

Filing systems within an organization cannot logically

communicate with one another unless there is a process involved.

All processes in DFD must be linked to either another process or

a data store.

DFD Errors

DFD is categorized as:Physical DFD

Shows how the system will be implemented including software, hardware, file, people etc.

Logical DFDShows how business operatesIt is concerned with how the system will be constructed.

Describes business events and data required and produced by the event

Advantages of Logical DFD Better communication with usersMore stable systems, since the design is based on a business framework

Increased understanding of the business by analysts

The system will have increased flexibility and be easier to maintain

Logical DFD to Physical DFD

Create a logical DFD of the current system

Next add all the data and processes not in the current system which must be present in the new system

Finally derive the physical data flow diagram for the new system

Data flow diagrams can be used to provide a clear representation of any business function.

The technique starts with an overall picture of the business and continues by analyzing each of the functional areas of interest.

This analysis can be carried out to precisely the level of detail required.

Who makes DFD tools? ConceptDraw - Windows and MacOS X data flow

diagramming tool Dia - Free source diagramming tool with flowchart

support Kivio - Free source diagramming tool for KDE Microsoft Visio - Windows diagramming tool which

includes very basic DFD support (Images only, does not record data flows)

SILVERRUN ModelSphere - cross-platform tool for business process modelling and data flow diagramming

SmartDraw - Windows diagraming tool with "Yourdon and Coad Process Notations" and "Gane and Sarson Process Notation"

Sample 1Overview of the System

The Electronic Flood Monitoring and Warning using SMS Technology (E-FMWS) for Brgy. Banago Bacolod City is a web-based and SMS early warning system designed and developed for the disaster committee, barangay officials, and residents of Brgy. Banago. The E-FMWS provides an early warning message and accurate typhoon advisory for the safety of the community and avoid loss of life and damage to properties. (Padernal, 2013)

Overview of the SystemThe E-FMWS includes several features for

the users of the system. These are: login/logout services for security purposes; real time status board for dissemination of current water level alert warning for each zone; SMS technology, to broadcast the alert warnings faster and quicker; user account management, to allow admin to register authorized users of E-FMWS and recipients of text messages; record archives, stores alert logs; and news and updates about disaster management and its projects.

(Sorongon, 2013)

Sample 2:Overview of the SystemThe Consumer Relation Management System

was designed and developed for CENECO, Bacolod City. The main objective of the study is to provide an automated system that will process the complaint of CENECO consumer. The system also generates statistical reports to determine what kind of complaint and services that is mostly rendered by CENECO to its consumers.

The features of the developed system are: User’s log-in/log-out; Reports; Utilities; Query Services; File Maintenance and Help Assistance.

(Gesulgon, 2012)

Use Case and DFDCreating a use case is another

approach used to develop a data flow diagram adapted from UML (Unified Modeling Language)

A use case is used to create a data flow diagram by providing a framework for obtaining processes, input, output, and data stores required for user activities

A use case shows the steps performed to accomplish a task

Use CaseThe major sections of a use case are

Use case nameDescriptionTriggerTrigger typeInput name and sourceOutput name and destinationSteps performedInformation required for each step

Use Case Format

References: http://en.wikipedia.org/wiki/Data_flow_diagram http://www.agilemodeling.com/artifacts/

dataFlowDiagram.htm http://www.edrawsoft.com/Data-Flow-

Diagrams.php Sommerville, Ian. Software Engineering, 7e. Sorongon, et. al. (2013). Flood Monitoring and

Warning System. Gesulgon, et. al (2012). Consumer Relations

Management System for CENECO.