SoberIT Software Business and Engineering Institute HELSINKI UNIVERSITY OF TECHNOLOGY 1 Requirements Engineering T Software Development Project I Sari Kujala

SoberIT Software Business and Engineering Institute HELSINKI UNIVERSITY OF TECHNOLOGY 2 Outline  Requirements engineering  Requirements gathering: interviewing  Requirements analysis

SoberIT Software Business and Engineering Institute HELSINKI UNIVERSITY OF TECHNOLOGY 3 What is Requirements Engineering (RE)?  The earliest phase of the software development life cycle  The goal is assure that a correct and good product is defined and developed from the stakeholders’ point of view  Possible stakeholders are customers, users, engineers responsible for system development and maintenance

SoberIT Software Business and Engineering Institute HELSINKI UNIVERSITY OF TECHNOLOGY 4 Why RE is important?  Detecting and correcting errors can be up to 200 times more expensive in the maintenance phase compared to the RE phase (Davis, 1993).  More time and effort invested in the early stages of a software project yields faster cycle times and higher productivity (Blackburn et al., 2000).

SoberIT Software Business and Engineering Institute HELSINKI UNIVERSITY OF TECHNOLOGY 5 Requirements in the Software Process Requirements definition Analysis & design & implementation & testing Acceptance testing Requirements management

SoberIT Software Business and Engineering Institute HELSINKI UNIVERSITY OF TECHNOLOGY 6 RE process (Kotonya & Sommerville, 1998)

SoberIT Software Business and Engineering Institute HELSINKI UNIVERSITY OF TECHNOLOGY 7 User Requirements  User requirements describe any function, constraint, or other property that must be provided to satisfy the user needs.  User requirements are written from user point of view (vs. technical requirements).

SoberIT Software Business and Engineering Institute HELSINKI UNIVERSITY OF TECHNOLOGY 8 User Requirements User requirements tell WHAT the system shall do from user’s point of view. Users are not interested in technical details. The system is seen as a black box. user group Auser group B

SoberIT Software Business and Engineering Institute HELSINKI UNIVERSITY OF TECHNOLOGY 9 Classification of requirements  Functional requirements define system functions  HERE: “the name of the high-level use case”  Non-functional requirements describe system qualities  User requirements describe the tasks that the user or another system will accomplish using the system  HERE: use cases

SoberIT Software Business and Engineering Institute HELSINKI UNIVERSITY OF TECHNOLOGY 10 Non-Functional Requirements  Look and Feel Requirements  Usability Requirements  Performance Requirements  Operational Requirements  Maintainability and Portability Requirements  Security Requirements  Cultural and Political Requirements  Legal Requirements

SoberIT Software Business and Engineering Institute HELSINKI UNIVERSITY OF TECHNOLOGY 11 Use cases (1/2) IDNimiPrioriteetti UC1SisäänkirjautuminenPakollinen UC2UloskirjautuminenPakollinen UC3Testausprojektin luominenPakollinen

SoberIT Software Business and Engineering Institute HELSINKI UNIVERSITY OF TECHNOLOGY 12 IDUse Case 1 NimiSisäänkirjautuminen TiivistelmäRekisteröityneen käyttäjän sisäänkirjautuminen ToimijatKaikki käyttäjät pois lukien asiakas Alkuehdot - Perussekvenssi 1.Järjestelmä kysyy identifiointia (käyttäjätunnus, salasana 2.Käyttäjä syöttää käyttäjätunnuksen ja salasanan 3.Järjestelmä tarkistaa käyttäjätunnuksen ja salasanan 4.Järjestelmä päästää käyttäjän sisään kirjautuvan käyttäjän oikeuksilla Poikkeukset 4a. Jos käyttäjätunnus ja salasana pari ei täsmää, järjestelmä tulostaa virheilmoituksen Jälkiehdot Käyttäjä on sisäänkirjautunut järjestelmään kyseisen käyttäjän oikeuksilla Viittaukset testitapauksiin ST-1, ST-2, ST-3

SoberIT Software Business and Engineering Institute HELSINKI UNIVERSITY OF TECHNOLOGY 13 Requirement gathering (or elicitation)  The goal is to understand  the domain area  the problem to be solved  the needs of the stakeholders

SoberIT Software Business and Engineering Institute HELSINKI UNIVERSITY OF TECHNOLOGY 14 Why customers and users are involved?  The goal of a new product is to solve a problem in the real world and users are experts in  problems to be solved  tasks to be supported  context and domain area  Involving users and customers as the source of information is related to project success and lower costs (Kujala et al., 2005).

SoberIT Software Business and Engineering Institute HELSINKI UNIVERSITY OF TECHNOLOGY 15 Requirements gathering in practice  Gather and check the existing material  Identify users and other stakeholders  Describe the main user groups  Gather customer and user needs by interviewing and observing  Document customer and user needs e.g. as a list  Record the source where the needs were gathered

SoberIT Software Business and Engineering Institute HELSINKI UNIVERSITY OF TECHNOLOGY 16 How to gather user needs? (1/2)  Select different users from different user groups: typical and advanced lead users  Watch, listen to, and talk with users in their own environment  Try to understand their goals and values, present ways of doing the tasks, underlying reasons for the behavior or wants

SoberIT Software Business and Engineering Institute HELSINKI UNIVERSITY OF TECHNOLOGY 17 How to gather user needs? (2/2)  Treat users as experts  Keep the conversation concrete  Ask users to show how they do things  Gather critical incidents (how it happened last time, yesterday)  Look at used notes, paper and pencil tasks, forms, modifications users have made

SoberIT Software Business and Engineering Institute HELSINKI UNIVERSITY OF TECHNOLOGY 18 Interviewing: questioning  Listen to interviewee, don’t be too quick in offering an interpretation  Ask one question at a time  Avoid leading and complex questions  Let user freely express himself, let a moment to think about

SoberIT Software Business and Engineering Institute HELSINKI UNIVERSITY OF TECHNOLOGY 19 Interviewing: information gathering  Ask the user first to tell about his/her work or situation generally  Try to understand the activities of the user  Use information that users provide as the basis for further questioning

SoberIT Software Business and Engineering Institute HELSINKI UNIVERSITY OF TECHNOLOGY 20 The language of customers and users  Remember that all kind of information is not easy to tell (e.g. skills)  Collect users terminology and use them (be careful not to use technical terms)  Make minimal assumptions about users and the information that they are giving  Also familiar terms can have different meaning for users