The problem of workflow instance migration occurs during dynamic evolutionary changes in processes. The paper presents a catalogbased algorithm called the Yo-Yo Algorithm for consistent instance migration in Petri net workflow models. It uses a technique of folding and unfolding of nets. The algorithm is formulated in terms of Colored Derivation Trees, a novel representation of the runtime states of workflow nets. The approach solves the problem for certain types of changes on acyclic block-structured workflow nets built in terms of primitive patterns moving much of the computation to schema level on account of the use of two critical ideas, a catalog and the folding order. The approach is illustrated with the help of examples and comments on its correctness.
Ahana Pradhan, Rushikesh K. Joshi