The development of GOMS modeling has continued, with progress in both
techniques and tools. Aversion called CPM-GOMS (CPM stands for both "cog-
nitive, perceptual, and motor" and "critical path method") can model the over-
lapping (multitasking) behavior displayed by extremely skilled users. It was
used to predict theefficiency ofa proposed workstation for telephone operators,
saving thecompany $2,000,000 a yearin operatingcosts. John and Kieras 0996a,
bl compare four variants of GOMS techniques and describe nine cases of their