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Week 3

Requirements Engineering Processes

Dr. Eman Al-MagharyDr. Eman Al-Maghary

Requirements EngineeringRequirements Engineering

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Requirements Engineering ProcessesProcesses

organized set of activities which transforms inputs to outputs

vehicle to communicate details of human activities

activities in a process may be enacted differently depending on the background of the people involved and the circumstances

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Design Processes (Cont.)

Processes which involve Creativity Interactions between a wide range of

different people Engineering judgment Background knowledge and experience

Inputs to the processes are not usually precisely defined

Many possible outputs may be defined to satisfy the inputs

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Design Processes (Cont.)

ExamplesProcess of writing a bookProcess of organizing a conferenceProcess of designing a processor chip

Requirements engineering process is a design process

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Requirements Engineering Process Inputs

1. Existing system information: Information about the functionality of the systems to be replaced or other systems which interact with the system being specified (* see example)

2. Stakeholder needs: Description of what stakeholders need from the system to support their work.**

3. Organizational standards: Standards used in an organization regarding system development, practice, quality management, etc..***

4. Regulations: external regulations such as health and safety regulations that apply to the system, or copy rights, data protection…****

5. Domain information : General information about the application domain of the system*****

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Requirements Engineering Process Output

1. Agrred Requirements2. System specification3. System models

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Requirements Engineering Process Variability

RE processes range from very unstructured processes to systematic processes

Factors influencing variability Technical maturity: The technologies and methods

vary from one organization to another. Disciplinary involvement: Types of engineers and

managerial involved in RE from one organization to another.

Organizational culture: as the culture varies so is the RE process

Application domain: Different types of applications require different types of RE processes

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Process ModelsA process model is a simplified description of a

processTypes of models

Coarse-grain activity models Sequencing mode Software life cycle model

Fine-grain activity models: more detailed process models

Role-action models: Show the role of different people involved in the process and the actions they take

Entity-relation models: Show process inputs, outputs and intermediate results

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ERM for the RE process

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Feasibilitystudy

Requirementselicitation and

analysisRequirementsspecification

Requirementsvalidation

Feasibilityreport

Systemmodels

User and systemrequirements

Requirementsdocument

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Requirements Engineering Process - Coarse-grain Activity Model

Activities Requirements elicitation Requirements analysis and negotiation Requirements documentation Requirements validation

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Requirements Engineering Process - Spiral Model

Different activities in requirements engineering are repeated until a decision is made to accept SRS

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Requirements Engineering Process Actors

People involved in carrying out the processRole-action diagrams show actors associated

with different process activities

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Human, Social and Organizational Factors - Stakeholders

May or may not have technical backgroundsHave other jobs and may not give priority to

requirements engineeringUsually have different goals - may not take

into account goals of other stakeholdersMay try to influence requirements to

maintain or increase political influence

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Human, Social and Organizational Factors – Stakeholders (Cont.)

Stakeholders software engineers: Responsible for system

development system end-users: Responsible for using the system

after delivery

managers of system end-usersProject manager: responsible of planning and

estimating the prototype project external regulators who check to make sure system

meets legal requirements domain experts: Responsible for providing

information about the application domain and problems specific to that domain which is to be resolved

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Requirements Engineering Process Support

Computer-Aided Software Engineering (CASE) tools support software design configuration management testing

CASE tools developed around the more understood portions of the lifecycle (not requirements engineering)

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Requirements Engineering Process Support (Cont.)

Modeling and validation tools used to specify the systemSADT, IDEF, PSL/PSA, etc.

Management tools manage a database of requirements RTM, CMVS

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Process ImprovementObjectives

Quality improvement Schedule reduction Resource reduction

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Process Improvement (Cont.)

Planning questionsWhat are the problems with current process?What are the improvement goals?How can we introduce process improvements

to achieve these goals?How should improvements be controlled and

managed?

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Process Improvement (Cont.)

Common requirements engineering process problemsLack of stakeholder involvementBusiness needs are not consideredLack of requirements managementLack of defined responsibilitiesStakeholder communication problems

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Process MaturityThe extent to which an organization

has defined its processes actively controls these processesprovides systematic human and computer-

based support for themAn organization with defined processes is

more mature than one with informal processes

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Process Maturity (Cont.)

Software Engineering Institute (SEI) Capability Maturity Model (CMM) five levels of maturityInitial - undisciplined (star personality)Repeatable - project oriented controlDefined - organization oriented controlManaged - measurements of both process

and product qualityOptimizing - continuous process

improvement strategy

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Requirements Engineering Process Maturity Model

Three Levels (on next slidesLevel 1 - InitialLevel 2 - RepeatableLevel 3 - Defined

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Requirements Engineering Process Maturity Model (Cont.)

Level 1 - Initial no defined process requirements engineering

process, it is left to individualsrequirements problems exist

excessive requirements volatility unsatisfied stakeholders large rework costs poor quality requirements documents over budget, missed schedule

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Level 2 - Repeatable Organizations have basic cost and schedule

management procedure predictions in the same application areadefined standards for requirements documentsdefined policies/procedures for requirements

management some advanced requirements engineering toolsmore likely to have quality documents on time

Requirements Engineering Process Maturity Model (Cont.)

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Level 3 - Defined Defined requirements engineering process

model based on good practices and techniquesActive process improvement program in placeMake objective assessments of the value of

new methods and techniques“ Have software process for both management

and engineering activities documented, standardized and integrated into software process for the organization”

Requirements Engineering Process Maturity Model (Cont.)