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Problem Frames 8 - Variant frames

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Problem Frames 8 - Variant frames. Variants. Model Operator Description Connection Control. Operator. Commanded Behavior is the operator variant of Controlled Behavior. Control machine. CM!C1. C3. Control Domain. Required Behavior. C. CD!C2. CM!C1. Control Domain. C3. CD!C2. - PowerPoint PPT Presentation
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Problem Frames 8 - Variant frames
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Page 1: Problem Frames 8 - Variant frames

Problem Frames 8 - Variant frames

Page 2: Problem Frames 8 - Variant frames

Variants

• Model

• Operator

• Description

• Connection

• Control

Page 3: Problem Frames 8 - Variant frames

Operator• Commanded Behavior is the operator

variant of Controlled Behavior

Control machine

Operator

C

B E4RM!E2

C3

CommandedBehavior

Control machine

ControlDomain

C

CD!C2

C3 RequiredBehavior

CM!C1

ControlDomain

CM!C1

CD!C2

Page 4: Problem Frames 8 - Variant frames

Commanded Information

Answering machine

Operator

C

B

Y4

Op!E5

C2

CommandedInformation

DisplayAM!E3

RW!C1

C

Real World

E5

Page 5: Problem Frames 8 - Variant frames

Commanded Workpiece?

Weird machine

Operator

B

B

E3

Op!E5

Y4

CommandedBehaviorUser

US!E3

WM!E1

X

Work Pieces

E5

WP!Y2

Page 6: Problem Frames 8 - Variant frames

Concern of operator variant

• Reject commands that are not sensible or not viable

• Carry out commands that are sensible and viable

Page 7: Problem Frames 8 - Variant frames

Description variant

• Model variant makes a lexical domain that describes part of a domain

• Description variant makes a lexical domain that describes part of the requirement

• Description domain is a set of rules that machine will interpret

• A virtual machine!

Page 8: Problem Frames 8 - Variant frames

Regulated One Way Lights

Regulated Controller

C

ER!{Phase,Duration}ER!{Char}

LU! {Go(I),Stop(I)}Conformity to regime

Light Units

RC! {Rpule(I),Gpulse(I)}

Encoded regime

LU! {Go(I),Stop(I)}

Page 9: Problem Frames 8 - Variant frames

Device Failure Detection

Failure Detector C

Report AD failure

ICU Patients

Patient Constraints

C

Failure Report

C

Analog devices

Page 10: Problem Frames 8 - Variant frames

Description Concern

• Must design description

• Requirements defines how to interpret description

• How does machine get new description?– Often there is another machine that edits it

Page 11: Problem Frames 8 - Variant frames

Connection variants

• Connection domain is between the machine and the domain that the requirements are about (the remote domain)

• New domains

• Changes specification of machine

• Does not change requirements

Page 12: Problem Frames 8 - Variant frames

Library controller

Members and candidates

Library staff

c Membership rules

Library controller

Members and candidates

Membership rules

Page 13: Problem Frames 8 - Variant frames

Payroll System

Payroll forms

Output

C

C d

a

b

c

Requirements for payroll

Page 14: Problem Frames 8 - Variant frames

Connection concerns

• Loss of information

• Errors

Page 15: Problem Frames 8 - Variant frames

Control variants

• For each shared event,– Which domain controls type?– Which domain controls time?– Which domain controls who participates?

• Reading a file– Machine controls time and participants– Workpiece controls the value (type of event)

Page 16: Problem Frames 8 - Variant frames

Control variant

Usage analyzer

ISP Softwarea

a: IS! {ISPOpen,ISPClose,ISPWrite}

Usage analyzer

Logfilesa

a: UA! {OpenLF, ReadLF} LF! {LogRecord(Read)}

Page 17: Problem Frames 8 - Variant frames

Conclusions

• Most variants add a domain

• Variants have their own concerns

Page 18: Problem Frames 8 - Variant frames

Particular Concerns

Problem Frames: Ch. 9

Page 19: Problem Frames 8 - Variant frames

Concerns

• Questions to ask

• Crucial in understanding the problem

• Frame concerns

• Variant concerns

• Particular concerns

Page 20: Problem Frames 8 - Variant frames

Particular Concerns

Concerns about a particular problem, not about a particular problem frame.

• Overrun

• Initialization

• Reliability

• Identities

• Completeness

Page 21: Problem Frames 8 - Variant frames

Overrun

• A domain’s ability or inability to respond to each externally controlled event before the next event occurs.

• Occurs when there is a mismatch of speeds at a domain interface.– Machine too fast– Machine too slow

Page 22: Problem Frames 8 - Variant frames

Strategies for slow machines

• Simple inhibition - the machine inhibits the shared events whenever it is not ready

• Ignoring - the machine ignores shared events whenever it is not ready

• Buffering - the machine buffers shared events whenever it is not ready, and participates later

Page 23: Problem Frames 8 - Variant frames

Initialization

• Machine has initial state

• Problem has initial state– only start machine when domain is in proper

state– machine sets state of the domain– machine learns state of the domain

• Model has initial state

Page 24: Problem Frames 8 - Variant frames

Reliability

• What happens when domain violates its description?

• Importance depends on– Likelihood of failure– Cost of failure

Page 25: Problem Frames 8 - Variant frames

Reliability

Separate problem of normal operation from problem of reliability

• Detection

• Diagnosis

• Repair

Page 26: Problem Frames 8 - Variant frames

Identities

• Identities concern is when the machine has an interface of shared phenomena with a set of individuals that – are not connected into any structure that

identifies them and– do not identify themselves.

Page 27: Problem Frames 8 - Variant frames

Identities

• Add a structure that identifies individuals

• Model– must be initialized– must be maintained

Page 28: Problem Frames 8 - Variant frames

Completeness

Does the machine do everything it is supposed to?

• Does a finite-state machine define what happens for every possible event?

• Does the description cover a large enough span?

Page 29: Problem Frames 8 - Variant frames

Increasing Description Scope

• Widen participation– X can do Y

• What else can it do?

• Can anything else do Y?

• Complementary events– For each event, can the opposite event happen?

Page 30: Problem Frames 8 - Variant frames

Particular Concerns

• Probably more

• A way to discover questions to ask

• Knowledge of experts


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