Some Models and Tools for Open Systems
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In computer science, there is a distinction between closed systems
whose behavior is totally determined in advance and open systems that
are systems that maintain a constant interaction with an unspecified
environment.  Closed systems are naturally modeled by transitions
systems.  %while open systems may be modeled as games.  Open systems
have been modeled in various ways, including process algebras, I/O
automata, ``modules'', and interfaces.  Games provide a uniform
setting in which all these models can be cast and compared. In this
extended abstract, we discuss the features and costs related to the
game-based approach to open systems, referring to some of the existing
models.  Finally, we describe a new model of interface, called
\emph{sociable interface}, which is geared towards easier
specification, improved reusability of models, and efficient symbolic
implementation.