Requirements Engineering Processes Objectives Topics covered Requirements engineering Feasibility studies

Requirements Engineering Processes Objectives Topics covered Requirements engineering Feasibility studies www.phwiki.com

Requirements Engineering Processes Objectives Topics covered Requirements engineering Feasibility studies

Smith, Peter, Morning On-Air Personality has reference to this Academic Journal, PHwiki organized this Journal Requirements Engineering Processes Objectives To describe the principal requirements engineering activities in addition to their relationships To introduce techniques as long as requirements elicitation in addition to analysis To describe requirements validation in addition to 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 in addition to analysis Requirements validation Requirements management

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Requirements engineering processes The processes used as long as RE vary widely depending on the application domain, the people involved in addition to 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 in addition to within budget; If the system can be integrated with other systems that are used. Feasibility study implementation Based on in as long as mation assessment (what is required), in as long as mation collection in addition to report writing. Questions as long as people in the organisation What if the system wasn’t 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 in addition to 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 in addition to the system’s 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 don’t know what they really want. Stakeholders express requirements in their own terms. Different stakeholders may have conflicting requirements. Organisational in addition to political factors may influence the system requirements. The requirements change during the analysis process. New stakeholders may emerge in addition to 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 in addition to organisation Groups related requirements in addition to organises them into coherent clusters. Prioritisation in addition to negotiation Prioritising requirements in addition to resolving requirements conflicts. Requirements documentation Requirements are documented in addition to input into the next round of the spiral.

Requirements discovery The process of gathering in as long as mation about the proposed in addition to existing systems in addition to distilling the user in addition to system requirements from this in as long as mation. Sources of in as long as mation include documentation, system stakeholders in addition to the specifications of similar systems. ATM stakeholders Bank customers Representatives of other banks Bank managers Counter staff Database administrators Security managers Marketing department Hardware in addition to 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 customer’s in addition to 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 in addition to security staff are indirect viewpoints. Domain viewpoints Domain characteristics in addition to constraints that influence the requirements. In an ATM, an example would be st in addition to ards as long as inter-bank communications. Viewpoint identification Identify viewpoints using Providers in addition to receivers of system services; Systems that interact directly with the system being specified; Regulations in addition to st in addition to ards; Sources of business in addition to non-functional requirements. Engineers who have to develop in addition to maintain the system; Marketing in addition to other business viewpoints. LIBSYS viewpoint hierarchy

Interviewing In as long as mal or in as long as mal interviewing, the RE team puts questions to stakeholders about the system that they use in addition to 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 in addition to a range of issues are explored with stakeholders. Interviews in practice Normally a mix of closed in addition to open-ended interviewing. Interviews are good as long as getting an overall underst in addition to ing of what stakeholders do in addition to how they might interact with the system. Interviews are not good as long as underst in addition to ing domain requirements Requirements engineers cannot underst in addition to specific domain terminology; Some domain knowledge is so familiar that people find it hard to articulate or think that it isn’t worth articulating. Effective interviewers Interviewers should be open-minded, willing to listen to stakeholders in addition to should not have pre-conceived ideas about the requirements. They should prompt the interviewee with a question or a proposal in addition to should not simply expect them to respond to a question such as ‘what do you want’.

Scenarios Scenarios are real-life examples of how a system can be used. They should include A description of the starting situation; A description of the normal flow of events; A description of what can go wrong; In as long as mation about other concurrent activities; A description of the state when the scenario finishes. LIBSYS scenario (1) LIBSYS scenario (2)

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Use cases Use-cases are a scenario based technique in the UML which identify the actors in an interaction in addition to which describe the interaction itself. A set of use cases should describe all possible interactions with the system. Sequence diagrams may be used to add detail to use-cases by showing the sequence of event processing in the system. Article printing use-case LIBSYS use cases

Article printing Print article sequence Social in addition to organisational factors Software systems are used in a social in addition to organisational context. This can influence or even dominate the system requirements. Social in addition to organisational factors are not a single viewpoint but are influences on all viewpoints. Good analysts must be sensitive to these factors but currently no systematic way to tackle their analysis.

Key points Social in addition to organisation factors influence system requirements. Requirements validation is concerned with checks as long as validity, consistency, completeness, realism in addition to verifiability. Business changes inevitably lead to changing requirements. Requirements management includes planning in addition to change management.

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