Maintaining semantic intention of step-wise operations in replicated CAD environments

Two kinds of operations are discovered in CoAutoCAD system: immediate one and step-wise one. The execution of the former (such as Line, Box etc.) is completed in one step while the latter(such as Mirror, Array) takes some continuous or discrete steps and the number of the steps can even not be predicted in some scenarios (such as Copy-Paste). So, during the execution process, the intention of the step-wise operations may be violated by concurrent operations coming from remote sites. This paper discusses the phenomenon and proposes to maintain the semantic intention of operations by introducing a novel approach called CLPF (Check Last Predict Future) to solve the violation happened before while predicting the future using the newly-updated information. In order to get the execution format of causally-ready operations, GOTO algorithm has been extended with VTfunction reflecting the influence of one operation on the other one.