Requirements Engineering Processes,Objectives,To describe the principal requirements engineering activities and their relationships To introduce techniques for requirements elicitation and analysis To describe requirements validation and the role of requirements reviews To discuss the role of requirements management in support of other requirements engineering processes,Topics covered,Feasibility studies Requirements elicitation and analysis Requirements validation Requirements management,Requirements engineering processes,The processes used for RE vary widely depending on the application domain, the people involved and the organisation developing the requirements. However, there are a number of generic activities common to all processes Requirements elicitation; Requirements analysis; Requirements validation; Requirements management.,The requirements engineering process,Requirements engineering,Feasibility studies,A feasibility study decides whether or not the proposed system is worthwhile. A short focused study that checks If the system contributes to organisational objectives; If the system can be engineered using current technology and within budget; If the system can be integrated with other systems that are used.,Feasibility study implementation,Based on information assessment (what is required), information collection and report writing. Questions for people in the organisation What if the system wasnt implemented? What are current process problems? How will the proposed system help? What will be the integration problems? Is new technology needed? What skills? What facilities must be supported by the proposed system?,Elicitation and analysis,Sometimes called requirements elicitation or requirements discovery. Involves technical staff working with customers to find out about the application domain, the services that the system should provide and the systems operational constraints. May involve end-users, managers, engineers involved in maintenance, domain experts, trade unions, etc. These are called stakeholders.,Problems of requirements analysis,Stakeholders dont know what they really want. Stakeholders express requirements in their own terms. Different stakeholders may have conflicting requirements. Organisational and political factors may influence the system requirements. The requirements change during the analysis process. New stakeholders may emerge and the business environment change.,The requirements spiral,Process activities,Requirements discovery Interacting with stakeholders to discover their requirements. Domain requirements are also discovered at this stage. Requirements classification and organisation Groups related requirements and organises them into coherent clusters. Prioritisation and negotiation Prioritising requirements and resolving requirements conflicts. Requirements documentation Requirements are documented and input into the next round of the spiral.,Requirements discovery,The process of gathering information about the proposed and existing systems and distilling the user and system requirements from this information. Sources of information include documentation, system stakeholders and the specifications of similar systems.,ATM stakeholders,Bank customers Representatives of other banks Bank managers Counter staff Database administrators Security managers Marketing department Hardware and software maintenance engineers Banking regulators,Viewpoints,Viewpoints are a way of structuring the requirements to represent the perspectives of different stakeholders. Stakeholders may be classified under different viewpoints. This multi-perspective analysis is important as there is no single correct way to analyse system requirements.,Types of viewpoint,Interactor viewpoints People or other systems that interact directly with the system. In an ATM, the customers and the account database are interactor VPs. Indirect viewpoints Stakeholders who do not use the system themselves but who influence the requirements. In an ATM, management and security staff are indirect viewpoints. Domain viewpoints Domain characteristics and constraints that influence the requirements. In an ATM, an example would be standards for inter-bank communications.,Viewpoint identification,Identify viewpoints using Providers and receivers of system services; Systems that interact directly with the system being specified; Regulations and standards; Sources of business and non-functional requirements. Engineers who have to develop and maintain the system; Marketing and other business viewpoints.,LIBSYS viewpoint hierarchy,Interviewing,In formal or informal interviewing, the RE team puts questions to stakeholders about the system that they use and the system to be developed. There are two types of interview Closed interviews where a pre-defined set of questions are answered. Open interviews where there is no pre-defined agenda and a range of issues are explored with stakeholders.,Interviews in practice,Normally