Petri net based modelling of procedures in complex object database applications

In this paper a new type of high level Petri nets is introduced for modelling procedures in complex object database applications. Places in these so-called nested relation/transition nets (NR/T-nets) represent schemes of unnormalized (nested) relations. The marking of each place is a nested relation of the respective type. Each transition represents a specific type of operation on the relations in the adjacent places. These operations may not only operate on whole tuples of a given relation but also on sub-tuples of existing tuples. Arcs in a net are inscribed with so-called filter tables which allow to formulate conditions on the specified (sub-) tuples. Each NR/T-net defines a class of possible system procedures