A Study on the OR decomposition of

goal-oriented analysis using GSN2014/09/17

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Agenda• 1.Introduction• 2.Related work• Representation of requirement- KAOS• Elicitation of requirements-The Owner Partitioned Goal Model• Notation of the evaluation process- GSN• The difference between our study

• 3. Proposal method• 4. Conclusion

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1.Introduction• Background：

• If any requirements are changed, the following process of the requirement analysis have to be change.=>Changing cost is so much.• So we do not want to change requirements.• But it must be happened.

• Because we live in uncertain world.• Business model change , Hardware change , Requirements have to be changed.

• Problem:• Which requirements are changed?

• If We can know that , we can prepare to the changing requirements.

• Force:• We can’t predict which requirements are changed

• Because we can’t predict the future.3

1.Introduction• Approach to solve the problem:• In order to solve this problem, we discuss how to acquire the requirements.

• Elicitation : From top goal , elicit the requirements by refinement repeatedly.• Choice: If there are conflicts between requirements , choice the requirements by evaluation.

• Evaluation and refinement are based on reasonable rationales.• If these rationales are not reliable, these rationales may be changed.• If these rationales are changed, Evaluation and refinement may be changed.• If evaluations and refinements may be changed , related requirements will be changed repeatedly.

• So if we know which requirements will be changed , we know the reliability of requirements’ rationales.• In this study, we discuss the evaluation process for choice.

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1.Introduction• In this Study , We propose• 1.A visualization method which will establish the reliability of the rationale for

the evaluation• 2.A visualization method being the re-evaluation and updating of the

requirements after evaluation.

• Before we propose the methods, we explain• the method of representation of requirements,• the method of elicitation of requirements,• the method of notation of the evaluation process

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2.Related work-Representation of requirement-KAOS

　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　

AND decomposition

OR decomposition

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All sub-goals are achieved -> the goal is achieved

At least one sub-goals is achieved -> the goal is achieved*Choice => OR decomposition

2.Related work- Elicitation of requirements-The Owner Partitioned Goal Model

http://www.computer.org/csdl/proceedings/apsec/2005/2465/00/24650130.pdf

Process1. Describe the

owner2. Describe each

owners requirements

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2.Related work- Notation of the evaluation process- GSN(Goal Structuring Notation)

http://www.goalstructuringnotation.info/documents/GSN_Standard.pdf

Notation for the process of argument by “goal” "strategy" (viewpoint) "context”

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Use for D-case Assurance case

2.The difference between our study• KAOS

• Enables notation of requirements.=>Use it• But it doesn’t enable to notate the reliability of the rationale for evaluation• And it doesn’t mention to elicitation of requirements.

• The Owner Partitioned Goal Model• Enables to elicit requirements.• We extended this method. Not only owner, But also other stakeholders.

• GSN• Enables to notate the evaluation process => Use It• But GSN is for assurance , not for requirements analysis=> extends it.• Extension 1 .We describe the goal not only supported goal by evidence but also not supported

goal by the rationale.• Extension 2. We describe the rationale and the reliability of it to the GSN’s evaluation.

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3. Proposal method• In order to establish the reliability of the rationale for the evaluation,

we operate the following process.• Describe the means.• Describe the stakeholder.• Describe each stakeholder’s requirements.• Describe the goal tree of whole system with GSN.• Evaluate and describe “the reliability of the rationale for the evaluation”.

• In order to show the re-evaluation point and updating of the requirements, we operate the following process.• When modifying, paint the modified part in gray.

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Ex: All the people can safely go over the road • Describe the means => stakeholders=> stakeholder’s requirements

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Conflict safety Reasonable price => choice

Means

Stakeholders

Requirements

Describe the goal tree of whole system with GSN• we evaluate the means by stakeholder's requirements

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Describe the goal tree of whole system with GSN• we evaluate the means by stakeholder's requirements

Requirements13

Stakeholders

Means

Describe the goal tree of whole system with GSN　• Evaluation• 1. We filled the value

of the contribution level in Table.• 2. The evidence of the

reliability of the rationale for the evaluation.

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3. Proposal method• In order to establish the reliability of the rationale for the evaluation,

we operate the following process.• Describe the means.• Describe the stakeholder.• Describe each stakeholder’s requirements.• Describe the goal tree of whole system with GSN.• Evaluate and describe “the reliability of the rationale for the evaluation”.

• In order to show the re-evaluation point and updating of the requirements, we operate the following process.• When modifying, paint the modified part in gray.

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Gray part=context => rationale change=>GSN have to be changeGray part=strategy=>GSN changed => KAOS have to be change.

Ex. “Neighborhood” was added as a new stakeholder.

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Ex. Modify on GSN

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Ex. Modify the stakeholder's requirement　

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Modify the GSN　

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4. Conclusion• The goal of this study : to show which requirements will be changed.• We assume that

• More; the requirements are changed • Less; the reliability of the rationale is low.

• We propose how to show the reliability of the rationale and re-evaluation point.• In particular we discuss the evaluation process of OR decomposition.

• As a result, • We described the evaluation process with GSN ,the reliability of the rationale and re-

evaluation point can be described.

• Future work• To make the tool of this method. • To describe of the reliability of the rationale for another factor.( i.e. requirements)

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