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Presentation on theme: "CHAPTER 15 – TASK ANALYSIS TYLER BRAZELL, MARC SMITH, MEGAN LISTER."— Presentation transcript:


2 INTRODUCTION What is task analysis?  Is the process of analyzing the way people preform the jobs: the things they do, the things, they act on, and the things they need to know.  Example:  In order to clean the house: 1.Get the vacuum cleaner out 2.Fix the attachment 3.Clean the rooms 4.When the dust bag gets full, empty it 5.Put the vacuum cleaner and tools away

3 DIFFERENCES BETWEEN TASK ANALYSIS AND OTHER TECHNIQUES Systems analysis vs. Task analysis system design - focus - the user Cognitive models vs. Task analysis internal mental state - focus - external actions practiced ‘unit’ task - focus - whole job

4 THREE APPROACHES TO TASK ANALYSIS  Task decomposition:  Which looks at the way a task is split into subtasks, and the order in which these are preformed  Knowledge-based techniques:  Which look at what the users need to know about the objects and actions involved in a task and how that knowledge is organized  Entity -relation -based analysis:  Which is an object-based approach where the emphasis is on identifying the actors and objects, the relationships between them and the actions they preform.

5 TASK DECOMPOSITION  Most task analysis techniques involve some form of task decomposition to express this sort of behavior.  Aims:  describe the actions people do  structure them within task subtask hierarchy  describe order of subtasks  Variants:  Hierarchical Task Analysis (HTA)  most common  Collaborative Task Tree (CTT) (CNUCE, Pisa)  uses LOTOS temporal operators

6 TEXTBOOK EXAMPLE Hierarchy description... 0. in order to clean the house 1. get the vacuum cleaner out 2. get 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

7 HOW TO GENERATE A HIERARCHY 1. Get list of tasks 2. Group tasks into higher level tasks 3. Decompose lowest level tasks further

8  How do we know when to stop?  Is “empty the dust bag” simple enough?  Purpose: expand only relevant tasks  Motor actions: lowest sensible level  P x C Rule  Says that the probability of making a mistake in the task is (p) times the cost of the mistake (C) is below a threshold, then stop expanding. STOPPING RULES

9 HTA PARSING SCENARIO get out cleaner fix carpet head clean dinning room clean main bedroom empty dustbag clean sitting room put cleaner away 1. 2. 3.2. 3.3. 3.2. 3. 4. 5. 0. 0. in order to clean the house 1. get the vacuum cleaner out 2. get 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

10  To better explain what is being talked about, here is a video of how to use hierarchal task analysis to set a table. HTA EXAMPLE

11 TYPES OF PLANS  fixed sequence - 1.1 then 1.2 then 1.3  optional tasks - if the pot is full 2  wait for events - when kettle boils 1.4  cycles - do 5.1 5.2 while there are still empty cups  time-sharing - do 1; at the same time...  discretionary - do any of 3.1, 3.2 or 3.3 in any order  mixtures - most plans involve several of the above

12 KNOWLEDGE –BASED ANALYSIS  Begins by listing all the objects and actions involved in the task and then building taxonomies (think about descriptions in biology) of them.  The aim is to understand the knowledge needed to preform a task and thus to help in the production of teaching materials and in assessing the amount of common knowledge between tasks.  Class Participation:  What would be considered an example of an everyday taxonomy?

13 KNOWLEDGE-BASED ANALYSIS EXAMPLE motor controls steering steering wheel, indicators engine/speed direct ignition, accelerator, foot brake gearing clutch, gear stick lights external headlights, hazard lights internal courtesy light wash/wipe wipers front wipers, rear wipers washers front washers, rear washers heating temperature control, air direction, fan, rear screen heater parking hand brake, door lock radio numerous!

14 TASK DESCRIPTION HIERARCHY (TDH)  Three types of branch point in taxonomy:  XOR–normal taxonomy object in one and only one branch  AND–object must be in both multiple classifications  OR–weakest case can be in one, many or none

15 ANOTHER TDH EXAMPLE kitchen item AND /____shape XOR / |____dished mixing bowl, casserole, saucepan, / | soup bowl, glass / |____flat plate, chopping board, frying pan /____function OR {____preparation mixing bowl, plate, chopping board {____cooking frying pan, casserole, saucepan {____dining XOR |____for food plate, soup bowl, casserole |____for drink glass NOTE: ‘/|{’ used for branch types.

16 ABSTRACTIONS AND CUTS  After producing detailed taxonomy, we can use these in order to produce generic descriptions of tasks  That is, ‘cut’ to yield abstract view  This is Knowledge Representation Grammar (KRG)  KRG terms opt for a generic description or generification.  One example is to break down a tree and make note to how many times a specific word is mentioned or used. If the number of occurrences is low, then one does not bother with the lower-level distinctions.  The choice of an appropriate level to “cut” the tree is also influence by the number of different sentences we get for a task.  If there are many, many sentences, we need to use generification.  Although if there are too few sentences, the level of abstraction is too great and needs to be revaluated.

17  Entity – relationship modeling is an analysis technique usually associated with database design and more recently object-oriented programming. ENTITY – RELATIONSHIP – BASED TECHNIQUES

18 OBJECTS  Start with list of objects and classify them:  Concrete objects (specifies):  simple things: spade, plough, glasshouse  Actors:  human actors: Vera, Sam, Tony, the customers  Composite objects (abstract):  sets: the team = Vera, Sam, Tony  tuples: tractor may be

19 ATTRIBUTES  To the objects, add attributes:  Example: Irrigation Pump  Attributes:  status: on/off/faulty  capacity: 100 litres/minute  Example: TVs  Attributes:  Status: On/Off/Stand By  Type: Low Def./ High Def./Smart TV

20 ACTIONS  Actions change the patient (the state of something)  Performed by the agent (someone or something)  There can be other attributes associated with an action  These are known as instruments  Example: “the gardener dug the soil with the spade”  Patient: Soil  Agent: Gardener  Instrument: Spade

21 EVENTS  Anything which happens  Actions performed are always events  Can also encounter spontaneous events  Example: The germination of a marrow seed  No agent is performing the germination  Some spontaneous events have no associated object at all  Example: Temperature changes  Events are also timed  Example: “At midnight”

22 RELATIONSHIPS  Tie objects, actions, and events together  Object-Object  Irrigation pump 3 is situated in the glasshouse  Action-Object  Vera tells Sam to dig the carrots with the spade

23 ATOM METHOD  Analysis for Task Object Modeling (ATOM)  Can be done in two ways  Analyze the order of subtasks and actions annotated by the objects involved  Refer to page 529  Can produce for any particular object a “life cycle” diagram representing all the actions in which it participates  Refer to page 530  Most methods include some notion of class or inheritance hierarchy

24 SOURCES OF INFORMATION AND DATA COLLECTION  Documentation  Observation  Interviews  Initial Analysis  Sorting and Classification

25 USES OF TASK ANALYSIS  Manuals and Tuition  Requirements Capture and Systems Design  Detailed Interface Deisgn

26 SUMMARY  There are several task analysis  Hierarchical task analysis decomposes a task into subtasks  Can be recorded either in a textual outline format or in a tree diagram  Knowledge based techniques built taxonomies of the objects used during a task and the actions performed upon them  Information for task analysis can be drawn from different sources  Analysis can be used to train and provide instruction

27 EXERCISE 15.6  This exercise is based on the mobile phone exercise on the book site:  A user interface designer analyzes Andy’s behavior with his original phone and realizes that both scenarios A and B are part of a general pattern, as shown in the hierarchical task analysis (HTA) in Figure 15.8. 1.Complete the HTA for phoning using the original phone taking into account scenarios A and B only briefly describe your solution. 2.Do a complete HTA for phoning using the new phone based on scenario C. 3.You will find that scenario C does not quiet fit into the general pattern in Figure 15.8. Discuss whether the solutions to 1 and 2 can be modified to emphasize their common features and whether this would clarify the over task description.





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