ABSTRACT
Currently, there are no effective methods of task analysis that can be efficiently used in the study of variable human activity. This is reflected in the two polarized approaches to task analysis: instruction-based approach and constraint-based approach. The instruction-based approach strictly determines all the required procedures of task performance. It is considered by some scientists as not being very efficient in contemporary task analysis. Vicente (1999) suggests resolving the apparent conflict between these approaches by introducing the concept of constraints, which specifies what should not be done by a performer. According to the second approach, performers independently decide how to perform the task within the existing constraints.
