Editing GOMS (section)

==Variations==

Basically there are five different GOMS models: the [[Keystroke-Level Model]], [[CMN-GOMS]], [[NGOMSL]], [[CPM-GOMS]], and SGOMS.
Each model has a different complexity and varies in activities.

===KLM===

The [[Keystroke-Level Model]] ('''KLM''') is the first and simplest GOMS technique [[Stuart Card]], [[Thomas P. Moran]] and [[Allen Newell]] created.<ref name="keystroke-level-model" />
Estimating an execution time for a task is done by listing the sequence of operators and then totaling the execution times for the individual operators. 
With KLM the analyst must specify the method used to accomplish each particular task instance. 
Furthermore, the specified methods are limited to being in sequence form and containing only keystroke-level primitive operators. 
The biggest difference between GOMS and [[Keystroke-level model|KLM]] is how time is assigned to cognitive and perceptual operators when it comes to execution time predictions.
Another major difference is that the goal-hierarchy is explicit in GOMS while it was implicit in the [[Keystroke-level model|KLM]].
The nature of unobservable operators is another important difference. [[Keystroke-level model|KLM]] has a single '''M''' operator that precedes each cognitive unit of action. In contrast, GOMS assigns no time to such cognitive overhead. But both models include '''M'''-like operators for substantial time-consuming mental actions such as locating information on the screen and verifying entries.
Both methods assign roughly the same time to unobservable perceptual and cognitive activities.
Also they make different assumptions about unobservable cognitive and perceptual operators and so distribute the time in different ways.<ref name="comparison" />
<ref name="technique">{{cite journal|title=Using GOMS for User Interface Design and Evaluation: Which Technique?|last=John |first=Bonnie E. |author2=David E. Kieras |journal=ACM Transactions on Computer-Human Interaction |publisher=[[Association for Computing Machinery|ACM]]|year=1996|location=[[United States of America]]|issn=1073-0516 | doi = 10.1145/235833.236050|s2cid=1187310 }}</ref>

KLM's execution part is described in four physical-motor operators:

* '''K'''  keystroking/ keypressing
* '''P'''  pointing with a mouse to a target
* '''H''' homing the hand on the keyboard
* '''D''' drawing a line segment on a grid

One mental operator '''M''' that stands for the time a user has to mentally prepare themselves to do an action, and a system response operator '''R''' in with the user has to wait for the system.
Execution time is the sum of the times spent executing the different operator types:

:''T''<sub>execute</sub> = ''T''<sub>K</sub> + ''T''<sub>P</sub> + ''T''<sub>H</sub> + ''T''<sub>D</sub> + ''T''<sub>M</sub> + ''T''<sub>R</sub>.<ref name="psychology" />

Each of these operators has an estimate of execution time, either a single value or a parameterized estimate.

==== Touch Level Model (TLM) ====
GOMS and it variants were designed for keyboard interfaces, nowadays a new type of interface is omnipresent.
This addition to the GOMS family, together with updates to the existing KLM operators, is called the Touch Level Model (TLM). 
[[Andrew D. Rice]] and [[Jonathan W. Lartigue]] propose this model for the used to model human task performance on a constrained input touchscreen device and, with proper benchmarking, accurately predict actual user performance.<ref>{{cite book|title=Touch-level model (TLM): evolving KLM-GOMS for touchscreen and mobile devices|last=Rice|first=Andrew D.|author2=Jonathan W. Lartigue|publisher=ACM|year=2014|isbn=978-1-4503-2923-1 | doi = 10.1145/2638404.2638532|s2cid=25139034 }}</ref>

The goal is to provide an instrument for quantitative analysis of touchscreen interfaces.

A number of operators are added for touchscreen interactions: 
; Distraction (X) : a multiplicative operator that is applied to other operators to model real world distractions
; Gesture (G) : gestures are conceptualized as specialized combinations of finger movements across the device's screen
; Pinch (P) : refers to the common two-finger gesture  
; Zoom (Z) : the reverse application of the Pinch operator. value in MS = 200 Ms
; Initial Act (I) : KLM assumed the user is prepared to begin an action, touchscreen devices require users to prepare them for use (home button or password)
; Tap (T) :  operator refers to the physical action of tapping an area on the touchscreen device in order to initiate some change or action
; Swipe (S) : usually a horizontally or vertically swipe like changing the page in a book. value in MS = 70 Ms
; Tilt (L(d)) : used  with an interacting with  a devices equipped with accelerometers.
; Rotate (O(d)) : gesture in which two or more fingers are placed on the screen and then rotated about a central point
; Drag (D) : similar to Swipe, Drag also involves tapping a location on the screen and then moving one or more fingers in specific direction

===CMN-GOMS===

'''CMN-GOMS''' is the original GOMS model proposed by [[Stuart Card]], [[Thomas P. Moran]] and [[Allen Newell]]. 

CMN stands for Card, Moran and Newell and it takes the KLM as its basic and adds subgoals and selection rules.
This model can predict operator sequence as well as execution time. A CMN-GOMS model can be represented in program form, making it amenable to analysis as well as execution. 
CMN-GOMS has been used to model word processors <ref name="psychology" /> and CAD systems for ergonomic design(see [[#CAD|CAD]]).
<ref name="comparison" /> 
The CMN method can predict the operator sequence and the execution time of a task on a quantitative level and can focus its attention on methods to accomplish goals on a qualitative level. 

In the example by [[Bonnie E. John]] and [[David E. Kieras]] a simple CMN-GOMS on editing a manuscript is shown.<ref name="comparison" />

{{pre|
GOAL: EDIT-MANUSCRIPT
. GOAL.  EDIT-UNIT-TASK ...repeat until no more unit tasks
. . GOAL.  ACQUIRE UNIT-TASK ...if task not remembered
. . .   GOAL.  TURN PAGE  ...if at end of manuscript
. . .   GOAL.  GET-FROM-MANUSCRIPT
. . GOAL.  EXECUTE-UNIT-TASK ...if a unit task was found
. . . GOAL.  MODIFY-TEXT
. . . .   select.  GOAL.   MOVE-TEXT* ...if text is to be moved
. . . . . .     GOAL.   DELETE-PHRASE ...if a phrase is to be deleted
. . . . . .     GOAL.   INSERT-WORD ... if a word is to be inserted
. . . .      VERIFY-EDIT
}}

Shown below is a simple copy and paste example.<ref>{{cite book|title=Analyse, Evaluierung und Optimierung der intraoperativen Mensch-Maschine-Interaktion|last=Voss|first=David|publisher=Eberhard-Karls-Universität Tübingen|year=2010|hdl=10900/45648 |url=http://hdl.handle.net/10900/45648}}</ref>
{{pre|
'''GOAL''' COPY-AND-PASTE-TEXT  

    '''GOAL''' COPY-TEXT
        '''GOAL''' HIGHLIGH-TEXT
            '''Operator''' MOVE-CURSOR-TO-BEGINNING
            '''Operator''' CLICK-MOUSE-BUTTON
            '''Operator''' MOVE-CURSOR-TO-END
            '''Operator''' SHIFT-CLICK-MOUSE-BUTTON
            '''Operator''' VERIFY-HIGHLIGHT
        '''GOAL''' ISSUE-COPY-COMMAND 
            '''Select*    '''
                '''GOAL''' USE-MOUSE
                    '''Operator''' MOVE-CURSOR-TO-EDIT-MENU
                    '''Operator''' PRESS-MOUSE-BUTTON
                    '''Operator''' MOVE-CURSOR-TO-COPY-ITEM
                    '''Operator''' VERIFY-HIGHLIGHT
                    '''Operator''' RELEASE-MOUSE-BUTTON
                '''GOAL''' USE-KEYBOARD
                    '''Operator''' PRESS-KEY-STRG
                    '''Operator''' PRESS-KEY-C
                    '''Operator''' RELEASE-KEYS
    '''GOAL''' PASTE-TEXT[...]

'''*''' Selection rule for '''GOAL''' ISSUE-COPY-COMMAND  

'''if''' HANDS-ARE-ON-KEYBOARD '''then''' 

    select '''GOAL''' USE-KEYBOARD
'''else''' 

    select '''GOAL''' USE-MOUSE

}}

===NGOMSL===

'''NGOMSL''' is a structured natural language notation for representing GOMS models and a procedure for constructing them. 
This program form provides predictions of operator sequences, execution time and time to learn methods.
An analyst constructs an NGOMSL model by performing a top-down, breadth-first expansion of the user's top-level goals into methods, until the methods contain only primitive
operators, typically keystroke-level operators. 
This model explicitly represents the goal structure just like the CMN-GOMS and can so represent high-level goals.<ref>{{cite book|chapter=GOMS modeling of user interfaces using NGOMSL|last= Kieras |first=David|title= Conference companion on Human factors in computing systems - CHI '94 |publisher=ACM|year=1994|pages= 371–372 |isbn=0-89791-651-4 | doi = 10.1145/259963.260467|s2cid= 16999909 }}</ref> 

Shown below is a simple example.<ref name="comparison" />

{{pre|
NGOMSL Statements 

'''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 COMMAND IS '''CUT''', AND 
            ACCOMPLISH GOAL     ISSUE A COMMAND
    '''STEP 3    ''' RETURN WITH GOAL ACCOMPLISHED

etc.
}}

===CPM-GOMS===

[[Bonnie E. John]] and [[David Kieras]] describe four different types of GOMS. CMN-GOMS, KLM and NGOMSL assume that all of the operators occur in sequence and do not contain operators that are below the activity level. 
CPM-GOMS being the fourth method uses operators at the level of [[Model Human Processor]] which assumes that operators of the cognitive processor, perceptual processor, and the motor processor can work in parallel to each other.
The most important point of CPM-GOMS is the ability to predict skilled behavior from its ability to model overlapping actions.
<ref>{{cite book|title=Automating CPM-GOMS|last=John.|first=Bonnie E.|author-link=Bonnie E. John |author2=Alonso Vera |author3=Michael Mattesa|publisher=ACM|year=2002|isbn=1-58113-453-3 | doi= 10.1145/503376.503404 |s2cid=675250 }}</ref>
<ref>{{cite book|title=CPM-GOMS: an analysis method for tasks with parallel activities|last=John|first=Bonnie E|author-link=Bonnie E. John |author2=Wayne D. Gray|publisher=ACM|year=1995|isbn=0-89791-755-3}}</ref>

===SGOMS===

SGOMS stands for Sociotechnical GOMS <ref>{{cite journal |last1=West |first1= R. L. |last2= Nagy|first2= N.|date=2007 |title=Using GOMS for Modeling Routine Tasks Within Complex Sociotechnical Systems: Connecting Macrocognitive Models to Microcognition |journal= Journal of Cognitive Engineering and Decision Making |volume= 1|issue= 2|pages= 186–211|doi= 10.1518/155534307X232848|s2cid= 62229701 }}</ref><ref>{{cite journal |last1=West |first1= R. L. |last2= Provnost|first2= S.|date=2009 |title= Modeling SGOMS in ACT-R: Linking Macro- and Microcognition |journal= Journal of Cognitive Engineering and Decision Making |volume= 3|issue= 2|pages= 194–207|doi= 10.1518/155534309X441853|s2cid= 62563894 }}</ref><ref>{{cite journal |last1=West |first1= R. L. |last2= Macdougal|first2= W.|date=2015 |title= The Macro Architecture Hypothesis: Modifying Newell's System Levels to Include Macro Cognition |journal= Biologically Inspired Cognitive Architectures }}</ref> and was created to allow GOMS to model work in complex sociotechnical systems. GOMS is meant to model an individual user, working in isolation, with no unexpected interruptions, similar to a Cognitive Psychology experiment. This level of analysis is sometimes referred to as ''microcognition'' to distinguish it from [[macrocognition]], which refers to real world cognition. SGOMS is meant to expand the applicability of GOMS to the macro cognitive level of analysis. To do this, SGOMS adds a high level control structure to GOMS, called the ''planning unit''. This allows GOMS to deal with unexpected interruptions.

A planning unit is a list of unit tasks. Planning units can be ordered (the unit tasks must be done in order) or situated (the unit tasks in the list are done as the situation demands). Consistent with [[CPM-GOMS]], SGOMS assumes that the agent can monitor the situation in parallel in order to detect threats (neurophysiologically, this function is associated with the [[amygdala]]). Planning units can be interrupted and bookmarked so they can be resumed later. When a planning unit is interrupted the agent considers the situation and can resume the same planning unit or bookmark it and switch to a different planning unit. SGOMS does not prescribe how this choice is made but, if the decision is based on routine expertise, it can be included in the SGOMS model.