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UFCE8V-20-3
Information Systems Development
SHAPE Hong Kong 2010/11
Lecture 3 : Hard Systems Modelling
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
2
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
3
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
4
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”
5
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
6
Data Flow Diagrams
• Process driven technique
• Used for modelling information processing
• Elements are…
– External entities
– Data stores
– Processes
– Data Flows
7
Data Flow Diagram (Context-Level 0)
Funding
Body
Funding
Opportunity
Funding
Decision
Application
Form
Potential
Client
Therapist
Referal
Recommendation
Terminate Treatment Contract
External
Therapist List
Assessment
Details
Client Details
Accept/Refuse
Assessment
Completed Application Form
Offer Of
Assessment
Application
Forms
Offer Treatment
Contract
Statistical
Report Request
ACPS
Management
Avon
Councelling
& Psychotherapy
Service
Statistics
Report
Update Client
Details
Accept Treatment Contract
Referal Details
Client
Decline Treatment Contract
Referal
Statistics
Interaction
Details
Interaction
Details
Terminate Treatment Contract
Referal
Statistics
Interaction
Details
Interaction
Details
Referal Details
Support
Service
Specific
Referals
Referal
Agent
Referal Request
8
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
9
Data Flow Diagram (Level 1)
Funding Opport unit y D et ails
Funding
Opport unit y
Funding
Body
D1
F unding Opport unit y
D et ails
M1
F unding Opport unit y
D et ails
AC PS
M anagement
Funding Opport unit y D et ails
Applic at ion
F orm
R eques t ed St at is t ic s R eport
St at is t ic s
R eport
Funding Opport unit y D et ails
Funding
D ec is ion
Funding Opport unit y D et ails
Funding Opport unit y D et ails
R eques t Applic at ion F orm
F unding Applic at ion
D2
H is t ory
F unding Applic at ion D et ails
C omplet ed Applic at ion F orm
Funding Opport unit y D et ails
3
Maint ain
Funding
D et ails
U pdat e Funding
Applic at ion D et ails
C opy Applic at ion F orm
M3
F unding Applic at ion D et ails
C opy Applic at ion F orm
F unding Applic at ion
F orm s
D3
F unding Applic at ion
H is t ory D et ails
F unding Applic at ion D et ails
U pdat e Funding
Applic at ion D et ails
R eques t ed
F unding D at a
F unding Applic at ion
F orm s
F unding Applic at ion D et ails
R eques t ed
F unding D at a
M2
F unding Applic at ion
H is t ory
D 4 F unding St at is t ic s
F unding Applic at ion
H is t ory D et ails
M 4 F unding St at is t ic s
C opy Applic at ion F orm
C opy Applic at ion F orm
AC PS
M anagement
F unding D at a
F unding D at a
St at is t ic al
R eport R eques t
R ef eral D et ails
AC PS
M anagement
St at is t ic s
R eport
4
C ollat e C lient
& Funding
St at is t ic s
R ef eral D et ails
R ef eral D et ails
D5
R ef eral
D eat ails
R ef eral
D et ails
M5
AC PS
M anagement
Support
Serv ic e
R ef eral D et ails
I nt erac t ion
D et ails
R ef eral D et ails
R ef eral D et ails
I nt erac t ion
D et ails
R ef eral
Agent
R ef eral R eques t
T herapis t
I nt erac t ion
D et ails
Ex t ernal
T herapis t Lis t
2
R ef eral
St at is t ic s
Maint ain
R ef eral
D et ails
C lient D et ails
As s es s ment
D et ails
R ef eral
St at is t ic s
Spec if ic
R ef erals
Support D et ails
Support
Serv ic e
R ef eral
Agent
Support D et ails
D8
R ef eral D et ails
D7
Support
D et ails
Pot ent ial C lient
D et ails
D6
C lient
D et ails
Pot ent ial As s es s ment det ails
C lient D et ails
Pot ent ial As s es s ment det ails
Pot ent ial
C lient
Of f er Of
As s es s ment
1
Maint ain
C lient
D et ails
R ef eral
R ec omm endat ion
Ac c ept / R ef us e
As s es s ment
T erm inat e T reat ment C ont rac t
T herapis t
U pdat e C lient
D et ails
T erm inat e T reat ment C ont rac t
Ac c ept T reat ment C ont rac t
C lient D et ails
D ec line Treat m ent C ont rac t
Of f er T reat ment
C ont rac t
C lient
C lient
10
Simple Example
Course
1
Student
Application
D1
Enrolment
Check
Course
Availability
Course availability
D2
2
Accept/Decline
Enrolment
Courses
Applications
Enrolment
Check
Applicant
Qualification
Application Details
Qualifications
11
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
12
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
13
Data Flow Diagram (Level 2)
D7
Potential
Client
Offer Of
Assessment
Potential
Client
Potential Client
Details
Accept/Refuse
Assessment
Potential Assessment details
Client
Offer Treatment
Contract
1
Maintain Client Details
1.1
Therapist
Decide
Potential
Client
Referal
Recommendation
Potential
Client Dtails
Decline Treatment Contract
1.2
Client
Create
Client
Client Details
1.3
Support
Service
Update
Client
Details
Referal Details
Terminate Treatment Contract
Client
Client Details
Client Details
Update Client
Details
Therapist
Accept Treatment Contract
Terminate Treatment Contract
D6
Client
Details
Client
Therapist
Client
14
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
15
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
16
Entity Attribute Relationship Diagram
(from normalised data)
D ISA B ILITY
ETH N IC _ OR IGIN
D ISA B ILITY_ ID
D ISABIL IT Y_D ESC R IPT IO N
OR IGIN _ ID
O R IG IN _D ESC R IPT IO N
EQU A L_ OPPOR TU N ITY
FOR M _N O
O R IG IN _ID
PAID _EM PL O YM EN T
EM PL O YM EN T _T YPE
SEXU AL_O R IEN T AT IO N
D ISABLED
D ISABIL IT Y_ID
R EG IST ER ED _D ISABLED
R EFER R EE
R EFER R EE_ ID
R EF ER R EE_N AM E
R EF ER R EE_AD D R ESS_ 1
R EF ER R EE_AD D R ESS_ 2
R EF ER R EE_AD D R ESS_ 3
R EF ER R EE_PO ST C O D E
R EF ER R EE_T EL EPH O N E_ N O
R EF ER R EE_F AX_ N O
R EF ER R EE_E-M AIL
R EF ER R EE_T YPE_ ID
R EFER R EE_ B OD Y
R EFER R EE_ TYPE_ID
R EF ER R EE_BO D Y_ AD D R ESS_ 1
R EF ER R EE_BO D Y_ AD D R ESS_ 2
R EF ER R EE_BO D Y_ AD D R ESS_ 3
R EF ER R EE_BO D Y_ PO ST C O D E
R EF ER R EE_BO D Y_ T ELEPH O N E_N O
R EF ER R EE_BO D Y_ F AX_N O
R EF ER R EE_BO D Y_ E-M AIL
POTEN TIA L_C LIEN T
C LIEN T
POTEN TIA L_C LIEN T_ ID
PO T EN T IAL_ C L IEN T _AG E
PO T EN T IAL_ C L IEN T _SEX
PO T EN T IAL_ C L IEN T _PO ST C O D E
R EF ER R EE_ID
ST AT ED _N EED _ C O M M EN T S
M ED IC AT IO N _ ID
D AT E_O F _ IN IT IAL_ C O N T AC T
G EN ER AL_PR AC T IT IO N ER _N AM E
G EN ER AL_PR AC T IT IO N ER _AD D R ESS_ 1
G EN ER AL_PR AC T IT IO N ER _AD D R ESS_ 2
G EN ER AL_PR AC T IT IO N ER _AD D R ESS_ 3
G EN ER AL_PR AC T IO N ER _PO ST C O D E
D EPEN D EN T _C H ILD _AG E_1
D EPEN D EN T _C H ILD _AG E_2
D EPEN D EN T _C H ILD _AG E_3
D EPEN D EN T _C H ILD _AG E_4
R EQ U IR ES_F U N D IN G
R ELAT IO N SH IP_ C O N C ER N S
ISO L AT IO N
LO SS
SEPAR AT IO N
O W N _ ST AT E
PH YSIC AL _ILL N ESS
D IF F IC U LT _EVEN T S
C H IL D R EN
N O _O F _C H ILD R EN
R EF ER R EE_T YPE_ N O
C LIEN T_N O
POTEN TIA L_C LIEN T_ ID
ASSESSM EN T _D AT E
SIN G LE_ PAR EN T
PAR EN T _ ST AT U S
R ISK_ASSESSM EN T _1
R ISK_ASSESSM EN T _2
R ISK_ASSESSM EN T _3
R ISK_ASSESSM EN T _4
D AT E_O F _ F IR ST _ SESSIO N
W O R K_ C AT EG O R Y_ID
C O N T R AC T _O F F ER ED
R EF ER R ED _O U T
R EF ER R AL_ O U T _ID
N AT U R E_O F _C O N T R AC T
W AS_C O N T R AC T _C O M PL ET ED
R EASO N _F O R _N O T _C O M PLET IN G
M ET _ ST AT ED _ N EED
APPR O PR IAT E_ SESSIO N _F O R _N EED
EST IM AT ED _N O _O F _SESSIO N S
W AS_C LIEN T _ F U N D ED
D AT E_SIG N ED _ O F F
EXTER N A L_TH ER A PIST
M ED IC A TION
M ED IC A TION _ID
M ED IC AT IO N _ D ESC R IPT IO N
R EFER R A L_ OU T_ ID
EXT ER N AL _T H ER APIST _ N AM E
EXT ER N AL _T H ER APIST _ AD D R ESS_1
EXT ER N AL _T H ER APIST _ AD D R ESS_2
EXT ER N AL _T H ER APIST _ AD D R ESS_3
EXT ER N AL _T H ER APIST _ PO ST C O D E
EXT ER N AL _T H ER APIST _ T ELEPH O N E_N O
EXT ER N AL _T H ER APIST _ F AX_N O
EXT ER N AL _T H ER APIST _ E-M AIL
W OR K _ C A TEGOR Y
W OR K _ C A TEGOR Y_ ID
W O R K_ C AT EG O R Y_D ESC R IPT IO N
W OR K _ A LLOC A TION
W OR K _ C A TEGOR Y_ ID
R EF ER R AL_ O U T _ID
17
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
18
Entity Life History
19
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.
20
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