CS 160 Lecture 5 Professor John Canny Fall

CS 160: Lecture 5 Professor John Canny Fall 2001 Sept 11, 2001 5/25/2021 1

Administrivia 4 You’re in a project group now (see the web site) 4 Make sure you meet this week and come up with a project proposal. 4 Hand in the proposal by Friday 5 pm. 5/25/2021 2

Task Analysis 4 A technique for analyzing existing tasks by observation. 4 Doesn’t require understanding of Users’ goals, just what they do. 4 But because of that its harder to apply to the design of a new system. * Good for training materials and documentation 5/25/2021 3

Task Analysis: 3 Approaches 4 Tasks decomposition: looks at how a task is split into subtasks and the order in which these are performed. 4 Knowledge-based techniques: what do users need to know about the objects and actions involved in a task? How is that knowledge organized? 4 Entity-relation-based analysis: an object-based approach, identify objects, relationships and actions. 5/25/2021 4

Task Decomposition 4 Break the task into subtasks: 4 Hierarchical Task Analysis (HTA): * Organize tasks into a hierarchy * Include ordering constraints * Looks something like logic programming (PROLOG) Clean house Get vacuum cleaner Clean hall 5/25/2021 Clean rooms Clean living room Empty dustbag Put everything away Clean bedrooms 5

Task Decomposition 0. In order to clean house * Get vacuum cleaner out * Fix attachment * Clean the rooms 3. 1 Clean the hall 3. 2 Clean the living rooms 3. 3 Clean the bedrooms * Empty the dustbag * Put the vacuum cleaner away Plan 0: Do 1 -2 -3 -5 in that order Plan 3: Do any of 3. 1, 3. 2, and 3. 3 in any order depending on which rooms need cleaning 5/25/2021 6

Task Decomposition Real tasks have more structure: 4 * * * Possible ordering of steps Frequency of steps Task achievement (all or some subtasks) 5/25/2021 7

Stopping Conditions P x C rule: 4 * * P is probability of a user error on the subtask C is the cost of the error 4 When P x C is small enough, we stop expanding 4 Can also stop at “skill” steps, where the users actions are not reflective (conscious) 5/25/2021 8

Task Variations 4 Optional tasks 4 Waiting for Events 4 Cycles 4 Time-sharing 5/25/2021 9

Aside: situated action Not all activities fit the task decomposition hierarchy nicely Think about tidying a room (vs. cleaning) 4 4 * * * 4 4 See an item, put it away Look at the arrangement of things, change it The arrangement of things suggests classifications. . . Your behavior is heavily influenced by the environment So don’t forget to observe real behavior when doing task analysis 5/25/2021 10

Knowledge-based analysis 4 4 Basic idea: start with list of items, then organize into a taxonomy (often ends up being a hierarchy) e. g. driving: * Steering wheel * Seat belt * Horn control * Seats * Windscreen * Speedometer * Dashboard * Steering column * Foot pedals. . . 5/25/2021 11

Knowledge-based analysis Controls: 4 * * Steering wheel Horn control Speedometer Foot pedals… Structural 4 * * * Seats + Seat belt Dashboard + Steering column Windscreen 5/25/2021 12

Knowledge-based analysis Controls: 4 * * Steering wheel Horn control Speedometer Foot pedals… Structural 4 * * * Seats + Seat belt Dashboard + Steering column Windscreen 5/25/2021 13

Producing a taxonomy 4 4 4 Start with an exhaustive list Using existing taxonomies (e. g. parts catalog) Put the items on cards - have users arrange them Taxonomies can be captured with attribute value pairs, some required, some optional TAKD (Task Analysis for Knowledge Description) produces a Task Descriptive Hierarchy (TDH). . 5/25/2021 14

TDH 4 Conjunctives: wash/wipe AND function XOR wipe front wipers, rear wipers wash front washers, rear washers position XOR front wipers, front washers rear wipers, rear washers 5/25/2021 15

More on TDH 4 TDH can be applied to actions as well as objects. 4 In comparison with HTA (Hierarchical Task Analysis), TDH Focuses on similarity of objects 4 HTA groups objects which are related by the task 4 HTA allows arbitrary repetition, TDH encourages uniqueness. 5/25/2021 16

KRG 4 Once we have a TDH, we can describe tasks in quasi-english sentences, using the TDH terms as standard nouns and verbs. 4 Idea is to describe the task at the right level of abstraction, with unambiguous terms. 4 Sounds a lot like XML. . . 5/25/2021 17

Entity-relationship techniques Borrowed from OO databases Objects 4 4 * * * Concrete Objects Actors Composite Objects Actions 4 * * Have at least a “patient” X (action is done to X) Often an “agent” (who does the action) May involve other objects “instruments” (agent) Sam planted the leeks (patient) with his spade (instrument) 5/25/2021 18

Objects 4 * * * Concrete Objects Actors Composite Objects 4 Composite objects are collections of objects “the team”, “the kit” - sets of things 4 Composite objects may also be “tuples”, e. g. an office comprises desks, chairs, file cabinets. . . 5/25/2021 19

Actions-messages Messages are a very important kind of action because they often influence other actions 4 * * * 4 People ask people to do things People commit to doing things We acknowledge completion of actions Speech-act theory studies this 5/25/2021 20

Entities and relationships Object Sam Actions: S 1: drive tractor S 2: dig carrots Relations: object-object location(pump 3, glasshouse) Relations: action-event before(plant seed, germinate) triggers(water seed, germinates seed) 5/25/2021 21

Sources of information 4 4 4 Existing documentation Observation in a worked example Interviews (create specific scenarios) 5/25/2021 22

Uses of task analysis 4 4 4 Manuals and documentation Requirements capture for design Detailed UI design 5/25/2021 23

Summary 4 4 Find your group members! Project proposals due Friday (JFC’s office mailbox) Task analysis is a way to understand work There are 3 different ways of approaching it (which can be used together to some extent) 5/25/2021 24