A method and an apparatus are provided for adjusting a sampling protocol in an
adaptive control process. The method comprises determining a performance value
based on a measurement associated with at least one or more previously processed
workpieces, adjusting a sampling protocol for one or more processed workpieces
based on the determined performance value, and measuring the one or more processed
workpieces according to the sampling protocol to provide one or more measurements.
The method further comprises adjusting at least one of a process model and a control
parameter based on at least a portion of the one or more measurements.