Requirements Gathering and Task analysis

Requirements gathering and task analysis 4 Requirements gathering is a central part of systems development understanding representation 4 Analysis involves understanding as well as representation of requirements functional, data usability 4 Requirements should include functional, data and usability requirements user-centred design 4 In user-centred approaches, requirements gathering almost always involves some design

Requirements Gathering Techniques 4 Traditional, Structured Methods use a toolkit of techniques for gathering requirements –input from client in the form of a Problem Statement –interviews, questionnaires, observation, document analysis 4 Functional Requirements modelled through Data - Flow Diagrams 4 Data requirements through Entity-Relationship Models

Traditional “life-cycle” model of software development Requirements GatheringRequirements Specification Design Implementation Maintenance

A User- centred approach to software development Evaluation Implementation Task analysis/ functional analysis Prototyping Requirements specification Conceptual design/ Formal design Star Model (Hartson & Hix)

User-Centred Approach 4 Analyst can additionally use cognitive and other task analysis techniques 4 Prototyping and Requirements animation can be used to facilitate requirements gathering 4 Object Technology has added Object/Class modelling and Use Cases to the toolkit 4 These techniques facilitate an approach which engages users throughout the lifecycle

Usability Requirements non-functional requirements 4 Core requirements are viewed as “black box” functions plus key non-functional requirements (e.g., speed of response etc.) 4 Usability requirements are often overlooked usability = “Any system designed for people to use should be easy to learn (and remember), useful, that is contains functions people really need in their work, and be easy and pleasant to use”(Gould and Lewis, 1985)

Components of Usability 4 Learnability –time and effort required to reach a specified level of performance 4 Throughput –tasks accomplished by experienced users, speed, number of errors etc. 4 Flexibility –system’s ability to respond to change 4 Attitude –positive feelings of users to the system

Components of a Usability Study 4 A Usability Study gathers Usability Requirements alongside functional, data specs. etc. and can involve –Usability Models –Usability Metrics –Usability Specifications

Task analysis 4 Describes behaviour at 3 levels –goals, tasks and actions 4 Tasks are usually viewed in terms of tasks and subtasks 4 Hierarchical Task Analysis 4 Hierarchical Task Analysis (HTA) focuses on what actually happens in terms of tasks and subtasks 4 Cognitive task analysis 4 Cognitive task analysis focuses on aspects of the cognitive characteristics of the users’ work

Goal-Task-Action 4 Goal (a.k.a. “external task”) –the state of the system the user wishes to achieve –e.g, produce a spreadsheet report, calculate payroll figures etc., 4 Task (a.k.a. “internal task”) –activities thought to be necessary to achieve the goal 4 Action –a task that involves no problem solving, or control structure

Hierarchical Task Analysis 4 Aim is to describe a task in terms of a hierarchy of operations and plans where –operations = Goal-Task-Action –plans = specification of conditions under which (sub) tasks are carried out 4 Can be captured graphically –using a form of structure chart

Partial HTA chart for Editing Text in Windows 0. Edit Text 1. Cut Text 1. Use Menu option 2. Use Hot-key Combo. 3. Use Toolbar Icon 4. Use Delete 1. Select Text2. Press Ctrl + X Plan 1.2: 1,2 Plan 1: According to Requirements

Hierarchical Task Analysis techniques 4 Starting 4 Starting the analysis –specify area of work or main task –break down into subtasks –draw subtasks out into layered plans 4 Progressing 4 Progressing the analysis –determine “granularity” of analysis –choose depth-first or breadth-first –document (notation in Preece p.415) 4 Finalizing 4 Finalizing the analysis –check for consistency, integrity –present to external “task expert” for confirmation