Requirement Enginering Software Requirement Tutorial 7

7/29/2019 Requirement Enginering Software Requirement Tutorial 7

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Requirements Engineering

Processes2

Lecture # 7


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Recap of Last Lecture - 1

We introduced the concept of

requirements engineering process

We discussed inputs and outputs ofthe requirements engineering process


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Recap of Last Lecture - 2

We introduced high-level activities in

the requirements engineering process

Requirements elicitation Requirements analysis and negotiation

Requirements specification

Requirements validation

Requirements management


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Todays Topics

Actors and stakeholders in the

requirements engineering process

Process and process improvement for

requirements engineering


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Who are Actors?

Actors in a process are the people

involved in the execution of that

process Actors are normally identified by their

roles rather than individually, e.g.,

project manager, purchasing director,and system engineer


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Actors in the RE Process - 1

Requirements engineering involves peoplewho are primarily interested in the problemto be solved (end-users, etc) as well as

people interested in the solution (systemdesigners, etc.)

Another group of people, such as health &

safety regulators, and maintenanceengineers may be effected by the existenceof the system


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Actors in the RE Process - 2

Role-action diagrams are process models

which show the actors associated with

different process activities

They document the information needs of

different people involved in the process

They use model of prototype softwaresystem as part of requirements elicitation

process


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Role-Action Diagram for

Software Prototyping

Understand

problem

Establish

outline

requirements

Select

prototyping

system

Develop

prototype

Evaluate

prototype

Req. EngineerDomain expert

End-user

Req. Engineer

End-user

SW Engineer

Project Mgr

Req. Engineer

SW Engineer

End-userDomain expert

Req. Engineer

SW Engineer

ACTIONS

ROLES


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Role Descriptions - 1

Role Description

Domain

Expert

Responsible for proving

information about theapplication domain and the

specific problem in that

domain, which is to be solved


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Role Description

System End-

user

Responsible for using the

system after delivery


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Role Description

Requirements

Engineer

Responsible for eliciting and

specifying the systemrequirements


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Role Description

Software

Engineer

Responsible for developing

the prototype software system


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Role Description

Project

Manager

Responsible for planning and

estimating the prototypingproject


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Human and Social Factors

Requirements engineering processes aredominated by human, social andorganizational factors because they always

involve a range of stakeholders fromdifferent backgrounds and with differentindividual and organizational goals

System stakeholders may come from arange of technical and non-technicalbackground and from different disciplines


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Stakeholder Types

Software engineers

System end-users

Managers of system end-users

External regulators

Domain experts


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Factors Influencing

Requirements

Personality and status of stakeholders

The personal goals of individuals

within an organization The degree of political influence of

stakeholders within an organization


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Process Support

One way to minimize errors in therequirements engineering is to use processmodels and to use CASE tools

The most mature CASE tools support well-understood activities such as programmingand testing and the use of structured

methods Support for requirements engineering is

still limited because of the informality andthe variability of the process


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CASE Tools for RE

Modeling and validation tools support the

development of system models which can

be used to specify the system and thechecking of these models for completeness

and consistency

Management tools help manage a database

of requirements and support the

management of changes to these

requirements


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RE Process Problems

Lack of stakeholder involvement

Business needs not considered

Lack of requirements management Lack of defined responsibilities

Stakeholder communication problems

Over-long schedules and poor qualityrequirements documents


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Requirements Engineering Costs

About fifteen percent (15%) of system

development costs

However, if the requirementsengineering process is not executed

properly, this cost can increase

substantially


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Summary

Human, social and organizational factorsare important influences on requirementsengineering processes

Requirements engineering processimprovement is difficult and is best tackledin an incremental way

Requirements engineering processes can beclassified according to their degree ofmaturity


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References

Requirements Engineering: Processes

and Techniques by G. Kotonya and I.

Sommerville, John Wiley & Sons,1998

Requirement Enginering Software Requirement Tutorial 7

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