The behavioral approach provides a mathematical language for the modelling
of systems, particularly dynamical systems. An introduction to behaviors is
given, with emphasis to interconnected systems. This is viewed as consisti
ng of modules, combined with an interconnection architecture. The latter is
formalized as a graph with leaves. The elimination theorem is discussed. T
his allows to obtain behavioral equations involving only manifest variables
, starting from models that contain also latent variables. Subsequently, th
e notions of controllability and observability are cast in this setting. (C
) 2000 IMACS. Published by Elsevier Science B.V. All rights reserved.