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Model based design NGOMSL and CPM- GOMS. NGOMSL. “Natural GOMS Language” Formal language with restricted English syntax The benefit of the formal language is that each statement roughly corresponds to a primitive mental chunk, so you can estimate the learning time (total execution time)
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NGOMSL • “Natural GOMS Language” • Formal language with restricted English syntax • The benefit of the formal language is that each statement roughly corresponds to a primitive mental chunk, so you can estimate the learning time (total execution time) • Addresses gaps in KLM modelling • Learning time measured by the # of NGOMS statements • It also has statements that represent working memory operations (retain and recall) • So the effective use of working memory can be estimated by executing this model
NGOMSL for move text • Method for goal: Move text • Step 1: Accomplish goal: cut text • Step 2: Accomplish goal: paste text • Step 3: Return with goal accomplished • Method for goal: cut text • Step 1: Accomplish goal: Highlight text • Step 2: Retain that the command is CUT, and accomplish goal: Issue a command (IC) • Step 3: Return with goal accomplished • Method for goal: paste text • Step 1: Accomplish goal: Position cursor at insertion point • Step 2: Retain that the command is PASTE and accomplish goal: IC • Step 3: Return with goal accomplished
CPM- GOMS • Cognitive Perceptual Motor or Critical Path Method is another variant of GOMS • Unlike KLM and other models (serial operations) CPM-GOMS model handles parallel operations • Ex: Point and shift-click
CPM- GOMS • It is more detailed than KLM • It tackles the serial assumption of KLM, allowing multiple operators to run at the same time • Uses parallel cognitive model • Each processor is serial • Different processors run in parallel
CPM- GOMS • CPM- GOMS have • A perceptual processor (PP) • A cognitive processor (CP) • Multiple motor processors (MP) one for each major muscle system that can act independently • For GUI interfaces, the muscles we mainly care about are the two hands and the eyes
The biology of the model Perceptual processor Cognitive processors Motor processors
Critical Path determines time • We build a CPM-GOMS for point-shift-click operation
CPM for point-shift-click • First, the cognitive processor (CP) which initiates everything decides to move the eyes to the pointing target • Next, the eyes actually move (MP eye), but in parallel with that, the CP is deciding to move the mouse • The right hand motor processor (MP right) handles it and the time is determined by the fitt’s law • While the hand is moving, the PP is in active and perceive both eyes and mouse move have found the target (perceive target and cursor blink)
CPM for point-shift-click • Then the CP verify the target and decides to press the shift key • This instruction is passes to the left hand motor processor (MP left) • MP left press the shift button
CPM GOMS-Critical Path Method • Critical path can be found though this graph of overlapping tasks • It can be defined as - the path that takes the longest time, since it will determine the total execution time for this method (model) • Note that this task would be just P and K in the KLM model • This model has minimize the errors (No errors) by parallelizing as much as possible