1. Model based design NGOMSL and CPM- GOMS

2. NGOMSL “Natural GOMS Language” Addresses gaps in KLM modelling
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

3. 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)
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

4. 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

5. 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

6. 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

7. The biology of the model
Perceptual processor
Cognitive processors
Motor processors

8. Critical Path determines time
We build a CPM-GOMS for point-shift-click operation

9. 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)

10. 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

11. 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

12. The end