Dealing with NFRs

Vahid Jalali

Amirkabir university of technology, Department of computer engineering and information technology, Intelligent systems laboratory, http://ceit.aut.ac.ir/islab, Requirement engineering course, Fall 2007

Three studies

Credit CardHealth

InsuranceTaxation

Accuracy

Performance

Security

User-friendlines

s

Amirkabir university of technology, Department of computer engineering and information technology, Intelligent systems laboratory, http://ceit.aut.ac.ir/islab, Requirement engineering course, Fall 2007

Process Vs. Product Quality of a product depends largely on the

quality of the process that leads form high level NFRs to the product

Complementary to the traditional product approach whose emphasis lies in product evaluation , usually involving metrics

Amirkabir university of technology, Department of computer engineering and information technology, Intelligent systems laboratory, http://ceit.aut.ac.ir/islab, Requirement engineering course, Fall 2007

NFR Framework Allows treating NFRs as potentially conflicting

or synergic goals to achieve Considering development alternatives which

could meet the stated NFRs Examining design tradeoffs Relating design decision to NFRs Justifying the decisions in relation to the

needs of the intended application domain Assisting defect detection

Amirkabir university of technology, Department of computer engineering and information technology, Intelligent systems laboratory, http://ceit.aut.ac.ir/islab, Requirement engineering course, Fall 2007

Goal Graph Structure Used for record and structure

NFRs Design alternatives Decisions rationale

Amirkabir university of technology, Department of computer engineering and information technology, Intelligent systems laboratory, http://ceit.aut.ac.ir/islab, Requirement engineering course, Fall 2007

Goal Graph Structure for Secure Document

U

UU

U

UU

U

SS

U

UU

U

S

U

Security

AccuracyConfidentiality

Availability

External Confidentiality

Internal ConfidentialityIdentification

IntConf(Small Accounts)

IntConf(large Accounts)

Access AuthorizationAuthentication

BiometricPassword

Card KeyIntConf

Vital Few Trivial Many

U User Friendliness

Amirkabir university of technology, Department of computer engineering and information technology, Intelligent systems laboratory, http://ceit.aut.ac.ir/islab, Requirement engineering course, Fall 2007

Sort HierarchyNFR Sort

User FriendlinessPerformance Security

Cost

Time

ResponseTime

Throughput

Space

MainMemory

SecondaryStorage

Confidentiality

Integrity

Availability

Accuracy

Internal ConsistencyExternal Consistency

Completeness

Operating CostDevelopment Cost

Amirkabir university of technology, Department of computer engineering and information technology, Intelligent systems laboratory, http://ceit.aut.ac.ir/islab, Requirement engineering course, Fall 2007

Where Specific NFRs come from? Development knowledge about specific NFRs

are to be taken from the literature and industrial experience and captured as methods, which are then presented for reuse to help the developers generate new goals and links

Amirkabir university of technology, Department of computer engineering and information technology, Intelligent systems laboratory, http://ceit.aut.ac.ir/islab, Requirement engineering course, Fall 2007

Methodology for Using NFR Framework Knowledge acquisition

Acquisition of knowledge specific to NFRs Academic industrial

Acquisition of domain knowledge organization

Application of the NFR-Framework Identification of NFR-related concepts

Identification of important NFR goals Identification of development techniques Identification of design rationale

Linking NFR-related concepts

Amirkabir university of technology, Department of computer engineering and information technology, Intelligent systems laboratory, http://ceit.aut.ac.ir/islab, Requirement engineering course, Fall 2007

Linking NFR-related Concepts Refining, clarifying and relating goals Identification of critical NFR goals Providing design rationale Assessing goal achievement

Amirkabir university of technology, Department of computer engineering and information technology, Intelligent systems laboratory, http://ceit.aut.ac.ir/islab, Requirement engineering course, Fall 2007

Refining, clarifying and relating goals Relating development techniques to NFR

goals Identifying conflict and synergy Clarifying the meaning of goals

Individually Associatively

Identifying factors underlying correlations

Amirkabir university of technology, Department of computer engineering and information technology, Intelligent systems laboratory, http://ceit.aut.ac.ir/islab, Requirement engineering course, Fall 2007

Identification of critical NFR goals Identifying what development techniques

were repeatedly emphasized Identifying critical goals and critical dominant

parts of the work load

Amirkabir university of technology, Department of computer engineering and information technology, Intelligent systems laboratory, http://ceit.aut.ac.ir/islab, Requirement engineering course, Fall 2007

Providing design rationale Locating applicable design rationale from

either the source document or workload description

Providing some design rationale from the basis of development tradeoffs present in goal graph structure under construction

Amirkabir university of technology, Department of computer engineering and information technology, Intelligent systems laboratory, http://ceit.aut.ac.ir/islab, Requirement engineering course, Fall 2007

Internal Evaluation When developers made aware of quality

concerns, that by itself helps improve the overall software quality

When conflicts and synergy among NFR goals were explicitly described, it is possible to consider design tradeoffs in selecting among alternatives

When competitive alternatives exist, expressing critical goals and the effect of each design decision helps resolving conflicts and record design rationale

Relating design rationale back to source NFRs which could improve traceability

Amirkabir university of technology, Department of computer engineering and information technology, Intelligent systems laboratory, http://ceit.aut.ac.ir/islab, Requirement engineering course, Fall 2007

Internal Evaluation (Cont.) Detecting faults

Ambiguity of goals Distinguishing goals into three types for detecting

omissions Antagonistic correlation rules help detecting

conflicts Detection of redundancies Synergic correlation helps in detecting

opportunities

Amirkabir university of technology, Department of computer engineering and information technology, Intelligent systems laboratory, http://ceit.aut.ac.ir/islab, Requirement engineering course, Fall 2007

Negative Findings Need for new decomposition methods Design rationale Qualitative approach Scalability of goal graph

Amirkabir university of technology, Department of computer engineering and information technology, Intelligent systems laboratory, http://ceit.aut.ac.ir/islab, Requirement engineering course, Fall 2007

Experts Evaluation Framework would be helpful for developers Improvements in naming and presentation are

needed to increase understandability Lack of consultation with domain people

during the study left gaps in domain knowledge

Applicability to broader domains Training costs and payoffs

Amirkabir university of technology, Department of computer engineering and information technology, Intelligent systems laboratory, http://ceit.aut.ac.ir/islab, Requirement engineering course, Fall 2007

Framework Findings Goal graph structures understandability Framework emphases Formality Process oriented approach Tradeoffs Determining main requirements

Amirkabir university of technology, Department of computer engineering and information technology, Intelligent systems laboratory, http://ceit.aut.ac.ir/islab, Requirement engineering course, Fall 2007

Application Domain Findings Domain knowledge and proportionality

Lack of contact with domain people Usage of framework

Amirkabir university of technology, Department of computer engineering and information technology, Intelligent systems laboratory, http://ceit.aut.ac.ir/islab, Requirement engineering course, Fall 2007

Conclusion NFR framework helps in presenting and using

large numbers of NFRs NFR representation helps in considering

design alternatives and their tradeoffs It is not clear that significantly larger studies

could be handled by NFR-assistant tool It is important to find a cost effective way for

training users work with framework

Amirkabir university of technology, Department of computer engineering and information technology, Intelligent systems laboratory, http://ceit.aut.ac.ir/islab, Requirement engineering course, Fall 2007

Reference Chung, L., Nixon, B.: Dealing with Non-

Functional Requirements :Three Experimental Studies of a Process-Oriented Approach. In: Proc. of ICSE’95, pp. 25–37. ACM Press (1995)

Amirkabir university of technology, Department of computer engineering and information technology, Intelligent systems laboratory, http://ceit.aut.ac.ir/islab, Requirement engineering course, Fall 2007

Thanks for your attention

Amirkabir university of technology, Department of computer engineering and information technology, Intelligent systems laboratory, http://ceit.aut.ac.ir/islab, Requirement engineering course, Fall 2007