A Petri net model for changing units of learning in runtime

In this paper, we present a Petri net-based approach that facilitates making structural changes at runtime to units of learning specified in IMS Learning Design (IMS LD). The proposed change model makes use of the hierarchical Petri net model derived from IMS LD and a page substitution mechanisms to replace learning flow components on the fly. As a result, a new hierarchical Petri net is defined, verifying that changes do not cause inconsistencies, such as data loss or errors, in the learning process. Furthermore, two change modes have been implemented: a safe mode, for conservative modifications that do not affect participants, and an unsafe mode, which may require to transfer the participant execution to a safe point in the new structure. Our approach has been developed as an extension of a Petri net-based IMS LD engine and validated with a set of real units of learning.