A flexible type checking model for stream interface binding

The need to type-check interfaces in support of safe and meaningful binding of interfaces is widely recognized. Unfortunately, complete interface conformance rules have been defined for operational (or procedural) interfaces only. Generally applicable conformance rules for interfaces featuring continuous media flows have so far proven harder to define partly due to the difficulty of deciding what form of subtyping and compatibility are most appropriate. In this paper we present the main ideas of a type model for continuous media flows. Furthermore we propose a scheme by which regular expressions can be used to declare flow compatibility policies of individual flows occurring in stream interfaces, and to relate flow types subject to different compatibility policies. A flow compatibility policy typically reflects a system's ability (or willingness) to adjust the structure and contents of its supported flow types to achieve flow end-point compatibility with some other system.