One of IS engineering problems – are analyses and simulation, in order to define users informative needs. Activity knowledge accumulation method and part of the system has been realized grounded on workflow models. System prototype has been created to extend CASE environment activity knowledge basis. The part of the system will be directly used by analysts, who will simulate the activity of computerized organization, trying to collect and analyze users information requirements. This work is a part of the scientific research “IS engineering method grounded on knowledge” carried out in the department of IS. Information systems engineering is started by the analyses of activity area – workflow model sequences of analyzed processes are made. Workflow model sequences transforming method has been created, that checks completeness and sequence of the data collected. Such checked by created methods and located in CASE system knowledge basis activity model will be called activity knowledge structure. In the storage of CASE system professional knowledge in accumulated and collected using modified work sequence models. The completeness of the information collected is checked using professional knowledge and completeness checking algorithms – information shift, data separation elimination of the breakpoints, function structure setting and import. The activity knowledge accumulation has been programmed. Information data accumulation and completeness checking algorithms are realized... [to full text]