CONTEXT of Context of the System(s) to be Developed

CONTEXT of Context of System(s) To Be Developed

Putcha V. Narasimham

Knowledge Enabler Systems

Context---Online Dictionary

• the set of circumstances or facts that surround a particular event, situation, etc.

http://dictionary.reference.com/browse/context?s=t

23SEP13Context of Context of STBD

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http://dictionary.reference.com/browse/set

What is off context is NOT shown

Context of Systems & Processes

Context is

1. What immediately surrounds referent

2. Specific to the referent

3. A close up view of the referent and its vicinity

4. NOT what is beyond


3

Context

Referent

Off Context or Irrelevant

For Correct Context Specification

The referent must be well-known at least as a black-box

Its internals may NOT be known (not shown)

It can be single or

Multiple—to be checked

What immediately surround the referent must be well-known and specified

The rest are deliberately ignored

4


SSAD Starts with Context Diagram

• The STBD .. a black-box

• No internal details are known / shown

• External Entities--independent of STBD

• Objects or Data flow between EEs and STBD


5

SystemTo Be

Developed

External

Entity 1

External

Entity 2

External

Entity 3

External

Entity n

OOAD Starts with Use Case Diagram

• System to be Developed STBD Provides named SERVICES

• Through separate Use Case Dialogs

• To each Role (Actor may play many roles)

• Leading to UC GOAL

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Use-case Name 1

Use-case Name 2

Use-case Name N

STBD Name

Syst

em

bo

un

dar

y

Act

or

: R

ole

Nam

e


Implied Assumptions

• STBD is just ONE

• An unverified implied assumption

• A Single STBD is often force fitted

• STBD may NOT be single

• It may consist of SEPARATE INDEPENDENT parts

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1

2

5

43

Force Fitting a Single STBD?

• What is assumed to be a Single STBD

• May be better modeled as

• Two or more independent &

separate Systems to be Developed

• See some examples

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12

5

4

3

Chess Game System

1. It is a game management software

2. Players are independent external entities

3. If 1 were to also play chess, would the software player be a part of 1 or separate?

A. Keep 1 &3 Separate?

B. Combine 1 & 3 ?

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1 Chess

Game

System 3 Software

Player

2 Human

Player

Airport Check-in Kiosk

1.Is it a separate system or a part of combination of three?

2.How are they related

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A:

Check-

in Kiosk

C:

Dispatch

Control

System

B:

Reservation

System

E-Shop

1.Is it a single system or separate systems?

2.How many?

3.Which of them can be combined

4.And which should NOT be combined?

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1 E-Catalog

& Shopping

Cart

3 Warehouse

2 Billing

4 Delivery

5 Returns

Relating the SYSTEMS to be developed

The SYSTEMS to be developed are named but HOW are they RELATED?


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1 Chess

Game

System3 Software

Player

2 Human

Player1 Check-

in Kiosk

3 Despatch

Control System

2 Reservation

System

1 E-Catalog &

Shopping Cart

3 Warehouse

2 Billing

4 Delivery

5 Returns

What is off CONTEXT is NOT shown

C

CONTEXT

CONTEXT of Context

1.At times we need to get a BIGGER picture

2.That is the CONTEXT of context

3.And the BIGGER Picture is:

4.TO BE PROCESS MAP

5.Can be a Class Diagram also


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Context

Referent

Off CONTEXT & Irrelevant

The BIGGER Picture: TWO possibilities

TO BE Process Map Class Diagram

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The BIGGER Picture: TO BE Process

• Provides a common visible & verifiable reference

• Makes implied assumptions and designs explicit

• Shows coupling and dependencies of entities and flows of objects, data and information

• Provides basis to assess and explore alternatives

• Exposes potential anomalies as modeling evolves

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Start with Business Deliverables

• Select Customers to be served

• Determine what they want i.e. the Business Deliverables

• Now work backward

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Evolve the TO BE Business Processes

Determine & Design What should be the Internal

Business Processes and

Inputs / Supplies

Get all stakeholders to agree

Now you have a well-designed TO BE Process

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Supplier

Organization

Business

Processes

cust

om

er


Real-world conditions +

Organizational policies and decisions

Shape the TO BE Process Some parts have to be

manual MP1-3 Some others can be

Automated AP1-5

TO BE Process--Manual & Automated 18

MP1

MP2

AP4

AP3

AP2

MP3

AP5

AP1

Exte

rnal in

puts

Busi

ness

Delivera

ble

s

Internal Outputs and Inputs

AutomatedManual


Further Partitioning of Automated Process

Partitioning criteria

Size (not applied)

Specialization, (not applied)

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MP1

MP2

AP4

AP3

AP2

MP3

AP5

AP1

Exte

rnal in

puts

Busi

ness

Delivera

ble

s


AutomatedManual


Further Partitioning of Automated Process

Partitioning criteria

Independence / Separable AP1 & AP2

Dependence / Coupling AP3, AP4 and AP5

So there are 3 STBDs

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MP1

MP2

AP4

AP3

AP2

MP3

AP5

AP1

Exte

rnal in

puts

Busi

ness

Delivera

ble

s


AutomatedManual


Context Diagram of AP1

A Context Diagram should have only ONE STBD,

Here AP1 has only two External Entities

Supplier (not shown) & MP2

Others are NOT in AP1’s context.

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MP2AP1

Exte

rnal in

puts


Context Diagram of AP2

A Context Diagram should have only ONE STBD, here AP2

AP2 has only two External Entities

MP2 and MP3

Others are NOT in AP2’s context.

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MP2 AP2

MP3


Context Diagram of AP3+AP4+AP5

The Context of STBD3 contains

3 External Entities

MP1, MP3 and External Customer (not shown)

Others are NOT in STBD3’s context.

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MP1

AP4

AP3 MP3

AP5

Busi

ness

Delivera

ble

s23SEP13Context of Context of STBD

Conclusion

• Context and Use Case Diagrams also have explicit logical basis for their creation & validity

• System To Be Developed is NOT always ONE

• There are criteria to determine and justify the number of Systems to be Developed

• Their utility, size and complexity can be estimated and managed with TO BE Process Maps

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Class Diagram can also be used for C of C

• Each Class has it’s own Context


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A

C

H

DB

G

E

F

Context of E: B & G

Context of A : C &F

Context of D: B, F & H

Some of A--H

maybe

combined

into one Unit

Design & Review Services

• Would be glad to create and or review the To Be Processes

• And proceed to identifying STBDs systematically

• Trial docs and demo sessions are free

[email protected]

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START


Technology

CONTEXT of Context of the System(s) to be Developed