Gary MarsdenSlide 1University of Cape Town Human-Computer Interaction - 5 Requirements Gary Marsden ( ) July 2002

Gary MarsdenSlide 2University of Cape Town Unit Objectives  We shall cover –Different forms of task analysis Procedure Based Object based Relationship based  Rationale: –In any lifecycle, it is important to get the problem defined well at the start Mistakes at this stage can be costly to rectify

Gary MarsdenSlide 3University of Cape Town Requirements Analysis  There are two things we need to say at the outset  Users don’t always know what they want  Programmers don’t always know what is best for users –Need methodology to understand the problem

Gary MarsdenSlide 4University of Cape Town Programmers are people?

Gary MarsdenSlide 5University of Cape Town What programmers see

Gary MarsdenSlide 6University of Cape Town Where to start  All lifecycles start by trying to quantify what the problem is  In HCI, we have a number of tools to do this –Analysis of the wider system (Task analysis) –Analysis of the user (human models) –Design guides and standards

Gary MarsdenSlide 7University of Cape Town Task Analysis  Common to most software engineering efforts  Focuses on the perspective of the user –what people do –what things they work with –what they must know

Gary MarsdenSlide 8University of Cape Town Example  In order to clean the house –get the vacuum cleaner out –fix the appropriate attachment –clean the rooms –when the dust bag gets full, empty it –put the vacuum cleaner and tools away  Must know about: –vacuum cleaners,their attachments, –dust bags, cupboards, rooms etc.

Gary MarsdenSlide 9University of Cape Town  Task decomposition –splitting task into (ordered) subtasks  Knowledge based techniques –what the user knows about the task and how it is organised  Entity/relation based analysis –relationships between objects and actions and the people who perform them  General method: –observe: unstructured lists of words and actions –organise: using notation or diagrams Different Approaches

Gary MarsdenSlide 10University of Cape Town Task Decomposition  Aims: –describe the actions people do –structure them within task subtask hierarchy –describe order of subtasks  Focus on Hierarchical Task Analysis (HTA). It uses: –text and diagrams to show hierarchy –plans to describe order

Gary MarsdenSlide 11University of Cape Town Example Decomposition  0. in order to clean the house –1. get the vacuum cleaner out –2. fix the appropriate attachment –3. clean the rooms 3.1. clean the hall 3.2. clean the living rooms 3.3. clean the bedrooms –4. empty the dust bag –5. put vacuum cleaner and attachments away ... and plans –Plan 0: do 1 { 2 { 3 { 5 in that order. when the dust bag gets full do 4 –Plan 3: do any of 3.1, 3.2 or 3.3 in any order depending on which rooms need cleaning  N.B. only the plans denote order

Gary MarsdenSlide 12University of Cape Town Generating hierarchy  get at list of tasks  group tasks into higher level tasks  decompose lowest level tasks further  Stopping rules –How do we know when to stop? –Is “empty the dust bag" simple enough?  Purpose: expand only relevant tasks  Error cost: stop when small  Motor actions: lowest sensible level

Gary MarsdenSlide 13University of Cape Town Diagrammatic Form

Gary MarsdenSlide 14University of Cape Town Knowledge-based Analysis  HTA is focused on procedures; KBA is based on objects and actions  Build taxonomy out of objects  Relationships are either: –XOR: exclusive –OR: In more than one branch –AND: Must have all branches

Gary MarsdenSlide 15University of Cape Town KBA example  Wash/wipe AND –Function XOR Wipe – Front wipers, rear wipers Wash – Front washers, rear washers –Position XOR Front – front washers, front wipers Rear – rear washers, rear wipers  Kitchen item OR –Preparation – mixing bowl, plate –Cooking – frying pan, saucepan –Dining – plate, glass

Gary MarsdenSlide 16University of Cape Town KBA applied  So what? Well, there is a close correlation between hierarchy and interface objects Where would you put “Insert Table”

Gary MarsdenSlide 17University of Cape Town Entity-Relationship  Very common technique, especially for databases  Won’t dwell on it here, but note that when used for HCI, includes non-computer objects  Good at identifying interface objects and functional relationships between objects

Gary MarsdenSlide 18University of Cape Town Outputs from task analysis  Procedural `how to do it' manual –from HTA description –useful for extreme novices –or when domain too difficult –assumes all tasks known  Conceptual manual –from knowledge or entity/relation based analyses –good for open ended tasks

Gary MarsdenSlide 19University of Cape Town More Output  Requirements capture and systems design –lifts focus from system to use –suggests candidates for automation –uncovers user's conceptual model  Detailed interface design –taxonomies suggest menu layout –object/action lists suggest interface objects –task frequency guides default choices –existing task sequences guide dialogue design  NOTE –task analysis is never complete –rigid task based design => inflexible system

Gary MarsdenSlide 20University of Cape Town Summary  We have looked at trying to understand the tasks of a particular problem –By considering the procedure of the task –By considering the objects used in the task –By considering the relationships between objects  We have also briefly looked at what purpose each type of analysis might be put to.