Using Event-Based Parsing to Support Dynamic Protocol Evolution

摘要

All systems built from distributed components involve the use of one or more protocols for intercomponent communication. Whether these protocols are based on a broadly used 'standard' or are specially designed for a particular application, they are likely to evolve. The goal of the work described here is to contribute techniques that can support protocol evolution. We are concerned not with how or why a protocol might evolve, or even whether that evolution is in some sense correct. Rather, our concern is with making it possible for applications to accommodate protocol changes dynamically. Our approach is based on a method for isolating the syntactic details of a protocol from the semantic concepts manipulated within components. Protocol syntax is formally specified in terms of tokens, message structures, delivery modes, and message sequences. Eventbased parsing techniques are used in a novel way to present to the application the semantic concepts embodied in these syntactic elements. We illustrate our approach by showing how it would support an HTTP 1.1 client interacting with an HTTP 1.0 server.