Dealing with NFRs Vahid Jalali Amirkabir university of technology, Department of computer engineering and information technology, Intelligent systems laboratory, Requirement engineering course, Fall 2007

Three studies Credit Card Health Insurance Taxation Accuracy PerformanceSecurity User- friendliness Amirkabir university of technology, Department of computer engineering and information technology, Intelligent systems laboratory, 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, 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, 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, Requirement engineering course, Fall 2007

Goal Graph Structure for Secure Document U U U U U U U S S U U U U S U Security Accuracy Confidentiality Availability External Confidentiality Internal ConfidentialityIdentification IntConf (Small Accounts) IntConf (large Accounts) Access Authorization Authentication Biometric Password Card Key IntConf Vital Few Trivial Many U User Friendliness Amirkabir university of technology, Department of computer engineering and information technology, Intelligent systems laboratory, Requirement engineering course, Fall 2007

Sort Hierarchy NFR Sort User Friendliness Performance Security Cost Time Response Time Throughput Space Main Memory Secondary Storage Confidentiality Integrity Availability Accuracy Internal Consistency External Consistency Completeness Operating Cost Development Cost Amirkabir university of technology, Department of computer engineering and information technology, Intelligent systems laboratory, 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, 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, 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, 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, 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, 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, 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, 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, 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, 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, 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, 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, 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, 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, Requirement engineering course, Fall 2007

Thanks for your attention Amirkabir university of technology, Department of computer engineering and information technology, Intelligent systems laboratory, Requirement engineering course, Fall 2007