T ask Analysis Ov erview What is task analysis? T ask Analysis Metho ds � task decomp osition � kno wledge based analysis � en tit y-relati onshi p tec hniques Sources of Information Uses of T ask Analysis Human{Com puter In teraction, Pren tice Hall T ask Analysis (1) A. Dix, J. Finla y , G. Ab o wd and R. Beale � c 1993 Chapter 7
What is T ask Analysis? Metho ds of analysing p eople's jobs: � what p eople do � what things they w ork with � what they m ust kno w Example: in order to clean the house get the v acuum cleaner out � �x the appropriate attac hmen t � clean the ro oms � when the dust bag gets full, empt y it � put the v acuum cleaner and to ols a w a y � Must kno w ab out: v accum cleaners,their attac hmen ts, dust bags, cupb oards, ro oms etc. Human{Com puter In teraction, Pren tice Hall T ask Analysis (2) A. Dix, J. Finla y , G. Ab o wd and R. Beale � c 1993 Chapter 7
Approac hes to task analysis � T ask decomp osition splitting task in to (ordered) subtasks � Kno wledge based tec hniques what the user kno ws ab out the task and ho w it is organised � En tit y{relat io n based analysis relationships b et w een ob jects and actions and the p eople who p erform them General metho d: � observe unstructured lists of w ords and actions � or ganize using notation or diagrams Human{Com puter In teraction, Pren tice Hall T ask Analysis (3) � c A. Dix, J. Finla y , G. Ab o wd and R. Beale 1993 Chapter 7
Di�erences from other tec hniques Systems analysis fo cus | system design T ask analysis fo cus | the user Cognitiv e mo dels fo cus | in ternal men tal state gran ularit y | practiced `unit' task T ask analysis fo cus | external actions gran ularit y | whole job Ho w ev er � m uc h o v erlap in general � di�erences ha v e exceptions. Human{Com puter In teraction, Pren tice Hall T ask Analysis (4) A. Dix, J. Finla y , G. Ab o wd and R. Beale � c 1993 Chapter 7
T ask Decomp osition Aims: � describ e the actions p eople do � structure them within task subtask hierarc h y � describ e order of subtasks F o cus on (HT A) Hier ar chic al T ask A nalysis It uses: � text and diagrams to sho w hierarc h y � plans to describ e order Human{Com puter In teraction, Pren tice Hall T ask Analysis (5) � c A. Dix, J. Finla y , G. Ab o wd and R. Beale 1993 Chapter 7
T extual HT A description Hierarc h y description ... 0. in order to clean the house 1. get the v acuum cleaner out 2. �x the appropriate attac hmen t 3. clean the ro oms 3.1. clean the hall 3.2. clean the living ro oms 3.3. clean the b edro oms 4. empt y the dust bag 5. put v acuum cleaner and attac hmen ts a w a y ... and plans Plan 0: do 1 { 2 { 3 { 5 in that order. when the dust bag gets full do 4 Plan 3: do an y of 3.1, 3.2 or 3.3 in an y order dep ending on whic h ro oms need cleaning N.B. the plans denote order only Human{Com puter In teraction, Pren tice Hall T ask Analysis (6) A. Dix, J. Finla y , G. Ab o wd and R. Beale � c 1993 Chapter 7
Generating the hierarc h y � get �at list of tasks � group tasks in to higher lev el tasks � decomp ose lo w est lev el tasks further Stopping rules Ho w do w e kno w when to stop? Is \empt y the dust bag" simple enough? expand only relev an t tasks Purp ose: stop when � is small Error cost: P C lo w est sensible lev el Motor actions: Human{Com puter In teraction, Pren tice Hall T ask Analysis (7) A. Dix, J. Finla y , G. Ab o wd and R. Beale � c 1993 Chapter 7
Diagrammatic HT A 0. make a cup of tea plan 0. do 1 at the same time, if the pot is full 2 then 3 - 4 after four or five minutes do 5 1. 2. 3. 4. 5. 6. put tea leaves pour in wait 4 or 5 boil water empty pot pour tea in pot boiling water minutes plan 1. 1.1 - 1.2 - 1.3 when kettle boils 1.4 1.1. 1.2. 1.3. 1.4. put kettle wait for kettle fill kettle turn off gas on stove to boil � Line under b o x means no further expansion. � Plans sho wn on diagram or written elsewhere. � Same information as: 0. mak e a cup of tea 1. b oil w ater : : : Human{Com puter In teraction, Pren tice Hall T ask Analysis (8) A. Dix, J. Finla y , G. Ab o wd and R. Beale � c 1993 Chapter 7
Re�ning the description Giv en initi al HT A (textual or diagram) Ho w to c hec k/impro v e it? Some heuristics: paired actions e.g., where is `turn on gas' restructure e.g., generate task `mak e p ot' balance e.g., is `p our tea' simpler than making p ot? generalise e.g., mak e one cup or t w o or more : : : Human{Com puter In teraction, Pren tice Hall T ask Analysis (9) � c A. Dix, J. Finla y , G. Ab o wd and R. Beale 1993 Chapter 7
Re�ned HT A for making tea 0. make cups of tea plan 0. do 1 at the same time, if the pot is full 2 then 3 – 4 after 4/5 minutes do 5 1. 2. 3. 4. 5. wait 4 or 5 boil water empty pot make pot pour tea minutes plan 5. empty for each NO 5.1 5.2 guest 5.3 cups ? YES plan 1. 1.1 – 1.2 – 1.3 – 1.4 when kettle boils 1.5 5.1. 5.2. 5.3. put milk fill cup do sugar in cup with tea plan 3. plan 5.3. 3.1 – 3.2 – 3.3 5.3.1 — if wanted 5.3.2 5.3.1. 5.3.2. 3.1. 3.2. 3.3. ask guest add sugar put tea leaves pour in about sugar to taste warm pot in pot boiling water 1.1. 1.2. 1.3. 1.4. 1.5. put kettle turn on and wait for kettle fill kettle turn off gas on stove light gas to boil Human{Com puter In teraction, Pren tice Hall T ask Analysis (10) A. Dix, J. Finla y , G. Ab o wd and R. Beale � c 1993 Chapter 7
T yp es of plan �xed sequence e.g., 1.1{1.2{1.3 optional tasks e.g., the p ot is full 2 if w aiting for ev en ts e.g., k ettle b oils 1.4 when cycles Plan 5. empty NO for each 5.1 5.2 cups ? guest 5.3 YES time-sharing e.g., do 1; at the same time : : : discretionary e.g., do an y of 3.1, 3.2 or 3.3 in any or der mixtures most plans in v olv e sev eral of the ab o v e Human{Com puter In teraction, Pren tice Hall T ask Analysis (11) A. Dix, J. Finla y , G. Ab o wd and R. Beale � c 1993 Chapter 7
Kno wledge Based Analyses F o cus on: | used in task Ob jects | p erformed Actions T axonomies represen t lev els of abstraction Example: motor con trols steering ste ering whe el, indic ators engine/sp eed direct ignition, ac c eler ator, fo ot br ake gearing clutch, ge ar stick ligh ts external he ad lights, hazar d lights in ternal c ourtesy light w ash/wip e wip ers fr ont wip ers, r e ar wip ers w ashers fr ont washers, r e ar washers heating temp er atur e c ontr ol, air dir e ction, fan, r e ar scr e en he ater parking hand br ake, do or lo ck radio n umerous! Human{Com puter In teraction, Pren tice Hall T ask Analysis (12) A. Dix, J. Finla y , G. Ab o wd and R. Beale � c 1993 Chapter 7
TDH notation TDH { T ask Description Hierarc h y Three t yp es of branc h p oin t in taxonom y: | normal taxonom y X OR ob ject in one and only one branc h | ob ject m ust b e in b oth AND represen ts m ultiple classi�cations | w eak est case OR can b e in one, man y or none Example: w ash/wip e AND function X OR wip e fr ont wip ers, r e ar wip ers w ash fr ont washers, r e ar washers p osition X OR fron t fr ont wip ers, fr ont washers rear r e ar wip ers, r e ar washers Human{Com puter In teraction, Pren tice Hall T ask Analysis (13) A. Dix, J. Finla y , G. Ab o wd and R. Beale � c 1993 Chapter 7
Larger TDH example kitc hen item AND / shap e X OR / dished j / mixing b ow l, c asser ole, sauc ep an, j / soup b ow l, glass j / �at j / plate, chopping b o ar d, frying p an function / OR preparation f f mixing b ow l, plate, chopping b o ar d co oking f f frying p an, c asser ole, sauc ep an dining f X OR for fo o d j j plate, soup b ow l, c asser ole for drink j glass N.B. ` /|{ ' used for branc h t yp es. Human{Com puter In teraction, Pren tice Hall T ask Analysis (14) � c A. Dix, J. Finla y , G. Ab o wd and R. Beale 1993 Chapter 7
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