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 and CAD systems for ergonomic design(see CAD). 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. 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. 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. Shown below is a simple example. 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