Requirements Gathering and Task analysis

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Requirements Gathering and Task analysis
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Requirements gathering and task analysis

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

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Requirements Gathering Techniques

• 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
• Functional Requirements modelled through Data
  -Flow Diagrams
• Data requirements through Entity-Relationship
  Models

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Traditional life-cycle model of software
development
Implementation
Maintenance
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A User- centred approach to software development
Task analysis/ functional analysis
Implementation
Requirements specification
Evaluation
Star Model (Hartson Hix)
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User-Centred Approach

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

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Usability Requirements

• Core requirements are viewed as black box
  functions plus key non-functional requirements
  (e.g., speed of response etc.)
• 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)

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Components of Usability

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

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Components of a Usability Study

• A Usability Study gathers Usability Requirements
  alongside functional, data specs. etc. and can
  involve
• Usability Models
• Usability Metrics
• Usability Specifications

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Task analysis

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

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Goal-Task-Action

• 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.,
• Task (a.k.a. internal task)
• activities thought to be necessary to achieve the
  goal
• Action
• a task that involves no problem solving, or
  control structure

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Hierarchical Task Analysis

• 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
• Can be captured graphically
• using a form of structure chart

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

• Starting the analysis
• specify area of work or main task
• break down into 4 - 8 subtasks
• draw subtasks out into layered plans
• Progressing the analysis
• determine granularity of analysis
• choose depth-first or breadth-first
• document (notation in Preece p.415)
• Finalizing the analysis
• check for consistency, integrity
• present to external task expert for confirmation