Requirements engineering iii
- 1. Requirements Engineering Indri Sudanawati Rozas Maret 2012
- 2. Activities? Feasibility Requirements study elicitation and analysis Requirements specification Feasibility Requirements report validation System models U and system ser requirements Requirements document
- 3. Elicitation
- 4. Elicitation • 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 system’s operational constraints • May involve end-users, managers, engineers involved in maintenance, domain experts, trade unions, etc. These are called stakeholders
- 5. Requirements Elicitation • Target – Stakeholders & user classes – System boundaries – Goals – Scenarios • Techniques – Interviews, questioners, surveys, meetings – Prototyping – Ethnographic techniques – Knowledge elicitation techniques – Conversation Analysis – Text Analysis
- 6. Activities within Elicitation • Define a requirements development process • Write a vision and scope document • Identify user classes and their characteristics • Select a product champion for each user class • Establish focus groups of typical users • Work with user requirements to identify use cases • Identify system events and responses • Hold facilitated elicitation workshops • Observe users performing their jobs • Examine problem reports of current system for requirement idea • Reuse requirements across projects
- 7. Problem with Elicitation • Stakeholders don’t 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
- 8. Difficulties of Elicitation • Thin spread of domain knowledge – The knowledge might be distributed across many sources • It is rarely available in an explicit form – There will be conflicts between knowledge from different sources • People have conflicting goals • People have different understanding of the problem • Tacit knowledge (The “say-do”problem) – People find it hard to describe knowledge they regularly use • Description may be inaccurate rationalizations of expert behaviour
- 9. Difficulties of Elicitation • Limited Observability – The problem owners might be too busy solving it using the existing system – Presence of an observer may change the problem • Bias – People may not be free to tell you what you need to know • Political climate & organizational factors matter – People may not want to tell you what you need to know • The outcome will affect them, so they may try to influence you (hidden agendas)
- 10. Elicitation Techniques Traditional techniques • Introspection • Reading existing documents • Analysing hard data (collection) • Interviews – Open-ended – Structured • Surveys / Questionnaires • Meetings
- 11. Elicitation Techniques Collaborative techniques • Group techniques – Focus Groups – Brainstorming • JAD/RAD workshops • Prototyping • Participatory Design
- 12. Elicitation Techniques Cognitive techniques • Task analysis • Protocol analysis • Knowledge Acquisition Techniques – Card Sorting – Laddering – Repertory Grids – Proximity Scaling Techniques
- 13. Elicitation Techniques Contextual approaches • Ethnographic techniques – Participant Observation – Enthnomethodology • Discourse Analysis – Conversation Analysis – Speech Act Analysis • Sociotechnical Methods – Soft Systems Analysis
- 14. Background Reading Sources of information: • company reports, organization charts, policy manuals, job descriptions, • reports, documentation of existing systems, etc. Advantages: • Helps the analyst to get an understanding of the organization before • meeting the people who work there. • Helps to prepare for other types of fact finding, e.g. by being aware of • the business objectives of the organization. • may tell you the detailed requirements for the current system. Disadvantages: • written documents often do not match up to reality. • Can be long-winded with much irrelevant detail Appropriate for • projects where analyst is not familiar with the organization being investigated.
- 15. Hard Data Collection Identify Collections of Hard Data • Facts and figures, financial information,… • Reports used for decision making,… • Survey results, marketing data,… Sampling • Sampling used to select representative set from a population – Purposive Sampling - choose the parts you think are relevant without worrying about statistical issues – Simple Random Sampling - choose every kth element – Stratified Random Sampling - identify strata and sample each – Clustered Random Sampling - choose a representative subpopulation and sample it
- 16. Hard Data Collection Sampling • Sample Size is important – balance between cost of data collection/analysis and required significance • Process: – Decide what data should be collected - e.g. banking transactions – Determine the population to be sampled - e.g. all transactions at 5 local branches over one week – Choose type of sample - e.g. simple random sampling – Choose sample size - e.g. every 10th transaction
- 17. Interviews Types: • Structured - agenda of fairly open questions • Open-ended - no pre-set agenda Advantages • Rich collection of information – Good for uncovering opinions, feelings, goals, as well as hard facts • Can probe in depth, & adapt followup questions to what the person tells you Disadvantages • Large amount of qualitative data can be hard to analyze • Hard to compare different respondents • Interviewing is a difficult skill to master Watch for • Unanswerable questions (“how do you tie your shoelaces?”) • Tacit knowledge (and post-hoc rationalizations) • Removal from context • Interviewer’s attitude may cause bias (e.g. variable attentiveness)
- 18. Questioners Advantages • Can quickly collect info from large numbers of people • Can be administered remotely • Can collect attitudes, beliefs, characteristics Disadvantages • Simplistic (presupposed) categories provide very little context • No room for users to convey their real needs Watch for: • Bias in sample selection • Bias in self-selecting respondents • Small sample size (lack of statistical significance) • Open ended questions (very hard to analyze!) • Leading questions ( “have you stopped beating your wife?”) • Appropriation ( “What is this a picture of?”) • Ambiguous questions (i.e. not everyone is answering the same question) Questionnaires MUST be prototyped and tested!
- 19. Meetings Used for summarization and feedback • E.g. meet with stakeholders towards the end of each stage: – to discuss the results of the information gathering stage – to conclude on a set of requirements – to agree on a design etc. • Use the meeting to confirm what has been learned, talk about findings Meetings are an important managerial tool • Used to move a system development project forward. • Need to determine objectives for the meeting: – E.g. presentation, problem solving, conflict resolution, progress analysis, gathering and merging of facts, training, planning,... • Plan the meeting carefully: – Schedule the meeting and arrange for facilities – Prepare an agenda and distribute it well in advance – The meeting itself may be structured or unstructured depending on objective; – Keep track of time and agenda during the meeting – Follow up with a written summary to be distributed to meeting participants – Special rules apply for formal presentations (and how to prepare them), project walkthroughs, brainstorming,...
Editor's Notes
- #6: Concerns the gathering of information (capturing requirements) Involves technical staff working with customers to find out about the application domain, the services that the system should provide and the system’s operational constraints May involve end-users, managers, engineers involved in maintenance, domain experts, trade unions, etc. These are called stakeholders (people who has some interests in the system development). In every case, a stakeholder has losses and gains and this could colour their viewpoint.