  In the paper notion of communication dualism id formalized and explained in
Petri net interpretation. We consider communication dualism a basic property of
communication in distributed systems. The formalization is done in the
Integrated Model of Distributed Systems (IMDS) where synchronous communication,
as well as asynchronous message-passing and variable-sharing are modeled in a
common framework. In the light of this property, communication in distributed
systems can be seen as a two-dimensional phenomenon with passing being its
spatial dimension and sharing its temporal dimension. Any distributed system
can be modeled as a composition of message-passes asynchronous processes or as
a composition of variable-sharing asynchronous processes. A method of automatic
process extraction in Petri net interpretation of IMDS is presented.
