Lecture 3 : Hard Systems Modelling

UFCE8V-20-3Information Systems Development

SHAPE Hong Kong 2010/11

Hard Systems Methods

• Rooted in systems thinking and draws on systems concepts

• Basis of most I.S. and I.T. design methodologies. For example…– Structured Systems Analysis and Design Methodology

(SSADM), Yourdon etc.• Takes a functional view of the organisation

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Underlying Assumptions

• There is a problem, the nature of which is agreed• There is general agreement about the nature of a

solution• The means of solving the problem involve the provision

of a new or redesigned computer based information system

• The problem solving process involves implementing formal modelling techniques within the framework of a methodology

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Characteristics• Usually a project life cycle based approach. For example…

– Requirements analysis• Model existing system• Look for weaknesses• Create model of improved system

– Designing– Constructing– Testing– Implementation– Maintenance

• Clear instructions and procedures for carrying out each stage

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Characteristics (2) – Strengths

• Distinct phases with “deliverables”• Can evaluate cost v benefits• Supports project management• Generates comprehensive documentation• May be supported by Computer Aided Systems

Engineering (CASE) tools• Historically has been the “industry standard”• Methods seen as either “data driven” or “process

driven”

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Characteristics (3) - Weaknesses• Unambitious system design• Failure to meet the needs of management• Instability• Inflexibility• User dissatisfaction• Problems with documentation• Lack of control• Incomplete systems• Application backlog• Maintenance workload• Problems with the “ideal” approach

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Data Flow Diagrams

• Process driven technique• Used for modelling information processing• Elements are…

– External entities– Data stores– Processes

– Data Flows

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Data Flow Diagram (Context-Level 0)

AvonCouncelling

& PsychotherapyService

Therapist PotentialClient

Client

SupportService Referal

Agent

ACPSManagement

FundingBody

FundingOpportunity

FundingDecision

ApplicationForm

Completed Appl-ication Form

ApplicationForms

StatisticalReport Request

Referal Details

StatisticsReport

Referal Request

InteractionDetails

ExternalTherapist List

Terminate Treat-ment Contract Assessment

Details

ReferalRecommendation

Client DetailsAccept/Refuse

Assessment

Offer OfAssessment

SpecificReferals

ReferalStatistics Interaction

Details

InteractionDetails

Terminate Treat-ment Contract

Decline Treatm-ent Contract

Offer TreatmentContract

Accept Treatme-nt Contract

Update ClientDetails

Referal Details

ReferalStatistics

InteractionDetails

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Data Flow Diagram (Context-Level 0)

• The top level diagram (level 0) models the whole system as a single process. The diagram identifies the following aspects of the system: -

• System boundary• All external entities• Related input and output flows

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Data Flow Diagram (Level 1)

A C P SM a nag e m e n t

S up por tS erv ic e

T he ra p is t

P o t en t ia lC lien t

R ef e ra lA ge n t

R ef e ra lA g en t

C l ien t

F u n d in gB od y

A C P SM an ag e m en t

S u pp or tS e rv ic e

T he ra p is t

M a in t a inC lie n tD e t a ils

1

M a in t a inR e fe ra lD e t a ils

2

M a in t a inF un d ingD e ta ils

3

C o lla te C lie n t& F un d ingS t a t is t ic s

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F u n d in g O ppo rt un it yD e ta ilsD 1

F u n d in g O ppo rt un it yD e ta ilsM 1

F un d ing A pp lic a t ionH is to ryD 2

F un d ing A pp lic a t ionH is to ryM 2

F u n d ing A pp lic a t ionF o rm sD 3

F und in g A p p l ic at ionF orm sM 3

F un d ing S ta t is t ic sD 4

F un d ing S ta t is t ic sM 4

A C P SM ana ge m en t

R ef e ra lD e a t a ilsD 5

R e fe ra lD e ta ilsM 5

C lie n tD e ta i lsD 6

P o te n t ia l C lie n tD e ta ilsD 7

A C P SM ana g em en t

S u pp or tD e ta ilsD 8

C lie n t

C om ple t ed A pp l-ic a t ion F orm

R efe ra l D e ta i ls

S ta t is t ic sR e por t

In t e rac t ionD e ta ils

R e fe ra l R eq ue s t

E x t e rna lT h e ra p is t L is t

A s s e s s m e n tD e ta ils

O f f e r O fA s s es s m e n t

S pe c if icR e fe ra ls

In te rac t ionD e ta ils

T erm in a t e T rea t -m en t C o n t rac t

D ec l ine T re a tm -en t C o n t rac t

O f f e r T re a tm en tC on trac t

F u nd ingO ppo rt un it y

S ta t is t ic a lR ep o rt R eq ues t

T erm in a t e T rea t -m e nt C o n t ra c t

R e fe ra lR e co m m e nd at io n

C lie n t D e ta ils

A c c ep t /R e f us eA s s e s s m en t

R efe ra lS ta t is t ic s

F u n d in g O p p ort -un it y D e ta ils

F un d ing O p por t -un it y D e ta i ls

F un d ing O p por t -un it y D e ta ils

F u n d in g O p po rt -un it y D e t a ils

F und in g A p p l ic -a t ion D e ta ils

F und ing A p p l ic -a t io n D e ta ils

F un d ing A pp lic -a t ion D e t a ils

C op y A p p l ic a t i-on F orm

C op y A p p l ic a t i-o n F o rm

C op y A p p lic a t i -on F orm

C op y A p p l ic a t i-on F orm

F un d ing D at a

R eq u es t edF un d ing D at a

F un d ing D a ta

R eq u es t edF un d ing D at a

S ta t is t ic sR epo rtR eq u es t ed S ta t -

is t ic s R e por t

F u n d in g O p po rt -un it y D e ta ils

F un d ing O p por t -u n it y D e ta ils

F un d in g A p p lic a t io nH is to ry D e ta i ls

F und ing A pp l ic a t ionH is to ry D e ta ils

R e fe ra l D e ta ils

R e fe ra l D e t a ils

R e fe ra l D e t a ils

R e fe ra l D e t a i ls

C lie n t D e ta ils

C lien t D e t ai ls

P o t e n t ia l A s s es -s m e n t de ta ils

P o t en t ia l A s s es -s m en t de ta ils

R ef e ra l D e t a ils

S u pp or t D e t a ils

S up por t D e t a ils

A c c e p t T re a t m e -n t C o n t rac t

F un d ing A pp lic -a t io n D e ta i ls

R equ es t A p p lic -a t ion F orm

F un d in gD ec is io n

A p p lic a t io nF orm

U pd a te F u nd in gA pp lic a t ion D e t a ils

U pd a t e F u nd in gA pp lic a t io n D e ta i ls

R efe ra l D e t ai ls

U pd a t e C lien tD e t a ils

In te rac t ionD e ta ils

R efe ra lS t a tis t ic s

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Simple Example

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StudentCheckCourse

Availability

CheckApplicant

Qualification

Courses

Applications

D1

D2

Qualifications

Application Details

Application

Accept/DeclineEnrolment

Course

Course availability

1

2

Enrolment

Enrolment

Data Flow Diagram (Level 1)

• The level 1 diagram gives an overview of the whole system. The diagram identifies the following aspects of the system: -

• Major system processes• Data flows between the processes• Data stores

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Resolution Levels

• Modelling a situation of any complexity can lead to huge models!

• The solution is to create hierarchies or “levels of resolution”

• Top more general – lower levels more detailed• Created by breaking a single element at an upper level

into a complete diagram at a lower level• Guideline: 7 +/- 2 elements on a single model

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Data Flow Diagram (Level 2)

Main ta in C lien t D e tails1

C lient

C lient

P o te ntialC lien t

C lien tD e tailsD 6

P o tentia l C lientD eta ilsD 7

T he ra pis t

P o tentia lC lie nt

T herap is t

T he ra pis t

C lient

S upportS ervic e

C lie nt

D e c id eP ote ntial

C lie nt

1 .1

C rea teC lient

1 .2

UpdateC lien tD e tails

1 .3

C lient

D ec lin e T rea tm -en t C o ntrac t

Te rm ina te T rea t-m ent C o ntrac t

O ffe r O fAs s es s m ent

C lien t D e ta ils

P o ten tia l As s e s -s m ent de ta ils

C lien t D e tails

Ac c ep t/R efus eAs s es s m e nt

T e rm ina te T rea t-m ent C ontra c t

R eferalR ec o m m en da tion

Ac c ep t T re atm e-n t C o ntra c t

R efe ra l D e ta ils

Up date C lie ntD e tails

P ote n tia lC lie nt D ta ils

C lien t D e tails

O ffe r T rea tm entC o ntrac t

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Data Flow Diagram (Level 2)

• Level 2 diagrams showing constituent system processes. The diagram identifies the following aspects of the system: -

• External entities to a specific process• Specific system processes• Data flows in and out of each process

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Other modelling – Entity Attribute Relationships (required for assignment)

• The following entity attribute diagram models the relationships between each database system entity. The diagram identifies the following aspects of the system: -

• Entity name• Items about which the system needs to store data• Internal structure of the entities• Relationships between entities that are significant to the

system

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Entity Attribute Relationship Diagram (from normalised data)

POTENTIAL_CLIENT_IDPOTENTIAL_CLIENT_AGEPOTENTIAL_CLIENT_SEXPOTENTIAL_CLIENT_POSTCODEREFERREE_IDSTATED_NEED_COMMENTSMEDICATION_IDDATE_OF_INITIAL_CONTACTGENERAL_PRACTITIONER_NAMEGENERAL_PRACTITIONER_ADDRESS_1GENERAL_PRACTITIONER_ADDRESS_2GENERAL_PRACTITIONER_ADDRESS_3GENERAL_PRACTIONER_POSTCODEDEPENDENT_CHILD_AGE_1DEPENDENT_CHILD_AGE_2DEPENDENT_CHILD_AGE_3DEPENDENT_CHILD_AGE_4REQUIRES_FUNDINGRELATIONSHIP_CONCERNSISOLATIONLOSSSEPARATIONOWN_STATEPHYSICAL_ILLNESSDIFFICULT_EVENTSCHILDRENNO_OF_CHILDRENREFERREE_TYPE_NO

POTENTIAL_CLIENT

REFERREE_IDREFERREE_NAMEREFERREE_ADDRESS_1REFERREE_ADDRESS_2REFERREE_ADDRESS_3REFERREE_POSTCODEREFERREE_TELEPHONE_NOREFERREE_FAX_NOREFERREE_E-MAILREFERREE_TYPE_ID

REFERREE

DISABILITY_IDDISABILITY_DESCRIPTION

DISABILITY

FORM_NOORIGIN_IDPAID_EMPLOYMENTEMPLOYMENT_TYPESEXUAL_ORIENTATIONDISABLEDDISABILITY_IDREGISTERED_DISABLED

EQUAL_OPPORTUNITY

ORIGIN_IDORIGIN_DESCRIPTION

ETHNIC_ORIGIN

MEDICATION_IDMEDICATION_DESCRIPTION

MEDICATION

REFERREE_TYPE_IDREFERREE_BODY_ADDRESS_1REFERREE_BODY_ADDRESS_2REFERREE_BODY_ADDRESS_3REFERREE_BODY_POSTCODEREFERREE_BODY_TELEPHONE_NOREFERREE_BODY_FAX_NOREFERREE_BODY_E-MAIL

REFERREE_BODY

REFERRAL_OUT_IDEXTERNAL_THERAPIST_NAMEEXTERNAL_THERAPIST_ADDRESS_1EXTERNAL_THERAPIST_ADDRESS_2EXTERNAL_THERAPIST_ADDRESS_3EXTERNAL_THERAPIST_POSTCODEEXTERNAL_THERAPIST_TELEPHONE_NOEXTERNAL_THERAPIST_FAX_NOEXTERNAL_THERAPIST_E-MAIL

EXTERNAL_THERAPIST

WORK_CATEGORY_IDREFERRAL_OUT_ID

WORK_ALLOCATION

CLIENT_NOPOTENTIAL_CLIENT_IDASSESSMENT_DATESINGLE_PARENTPARENT_STATUSRISK_ASSESSMENT_1RISK_ASSESSMENT_2RISK_ASSESSMENT_3RISK_ASSESSMENT_4DATE_OF_FIRST_SESSIONWORK_CATEGORY_IDCONTRACT_OFFEREDREFERRED_OUTREFERRAL_OUT_IDNATURE_OF_CONTRACTWAS_CONTRACT_COMPLETEDREASON_FOR_NOT_COMPLETINGMET_STATED_NEEDAPPROPRIATE_SESSION_FOR_NEEDESTIMATED_NO_OF_SESSIONSWAS_CLIENT_FUNDEDDATE_SIGNED_OFF

CLIENT

WORK_CATEGORY_IDWORK_CATEGORY_DESCRIPTION

WORK_CATEGORY

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Other modelling – Entity Life Histories

• Entity Life History Diagrams• The following entity life history diagram models the

movement of data through the system at various levels of detail. This diagram identifies the following aspects of the system: -

• Event sequencing• Event iteration• Event order and timing

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Entity Life History

Summary

• Structured methods provide a framework to:– Aid communication– Provide a set of techniques that standardises an

approach and is proven– Identifies errors– Eliminates ad-hoc problem solving– Ensures sufficient effort is put into the analysis

stage.

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