Requirements Gathering : Determining the scope of the system 1. Elicitiation – fact finding 2. Specification 3. Validation

Problem-solving model Sense Gather data Listen Examine Problem (Re) Definition Question Finding ideas Finding and evaluating Solutions Implement and evaluate solution

Defining the scope….. Functional requirements Non- functional requirements Hardware, software constraints Security Performance e.g. Response time Integration reliability Quality - ISO standards can provide checklists here.

Requirements Elicitation Techniques –Interviews –Questionnaires –Existing Documentation – forms, reports etc. –Observation –Structured meetings e.g. participatory design

Requirements Elicitation:aim To find out as much as possible about the business requirements for the system.

Interviewing Identify initial stakeholders, actors in system and find out their requirements. Identify who the stakeholders are. Plan –list objectives, subjects, topics, questions, strategy –organise time and location –list what documents should be brought to the interview Conduct Interviews – listen, validate, record What types of information can you find?

Interviews What are the users trying to accomplish and why? Plan and prepare well Have clear objectives Work out structure and questions in advance

Observation Watching people doing their jobs shows: exception situations, interruptions problems time taken to complete tasks might give you an idea of what problems the new system could solve.

Questionnaires Good for finding out information from large groups of people or geographically disparate groups.

Documenting Requirements Filter out relevant issues and record them in an appropriate form e.g. –Context Diagram –DFDs –E-R diagrams –Use-Case diagrams –Textual descriptions Desirable Characteristics of specification –Correctness –Consistency –Completeness –Understandability

Context Diagram Shows inputs and outputs to system and the sources/recipients of these Student registration system student lecturer Registration details Student ID Class list Module code Course designer Course details

Entity- Relationship diagram Shows key entities and their relationships student course module

Data Flow Diagram Shows business processes, information flows and data stores 1.0 input student details 2.0 process student details 3.0 Generate new student number Student file Course file Student record 5.0 Print student card Student card student Student record Student details Student number 4.0 Check course eligibility Course code Course record Yes/no Course code, Student details

Decision Tables Wee k night YYYNNN… Seaso n HHHHHH… Roo m type famdblsngfamdblsng… Price €100€80€60€120€90€75 …

Use Case Diagrams Business requirements – essential use cases Guest Order food/ drink Book spa Request alarm call Hotel self service subsystem Check valid room number >

Each Use Case Describes a system function from a user’s perspective Details business events and users interaction with the system during that event Represents a system activity, a well-defined part of the system’s functionality Has a goal Supported by behaviour specifications (templates) Has a more detailed description, possibly specifying a number of scenarios or alternate courses of action

Use cases are initially defined at a high level and successively refined as the analysis and software development process unfolds. Essential use case – key business requirements Real Use Case – more detail about what actually happens What are the users trying to accomplish and why?