We describe the design and implementation of the Concert/C compiler and runtime. We describe solutions to the problems of (1) how to extend a language without compromising the use of legacy source and object code and tools, (2) how to extract language-neutral interface information from native language type declarations, (3) how to make function pointers into first-class values transmissable over a network while retaining runtime compatibility with plain C, and (4) how to interoperate with multiple RPC and messaging protocols, selecting protocols at runtime, with little sacrifice of efficiency.>

Optimistic failure recovery mechanisms are proposed as a way to provide transparent fault tolerance to distributed applications and systems. The authors identify problems that may arise when these mechanisms are applied to vast networks including many processors and spanning large geographical areas and many administrative domains. They present a technique-recovery unit gateways-that can be used to address many of these issues with existing failure recovery algorithms. This method can be applied with minimal disruption to existing transparent recovery systems, as well as to build large optimistic recovery systems while minimizing the dependency tracking overhead.>

G. Higman's lemma (1952) is a special case of the more general Kruskal's tree embedding theorem and the graph minor theorem. A direct constructive proof of the lemma with manifest computational content is presented. This is done by reducing the problem to a construction of certain sets of sequential regular expressions. A well-founded order on such sets is exhibited, and the lemma then follows by induction.>

In this paper we investigate generalizations of Kahn's principle to nondeterministic dataflow networks. Specifically, we show that for the class of "oraclizable" networks a semantic model in which networks are represented by certain sets of continuous functions is fully abstract and has the fixed-point property. We go on to show that the oraclizable networks are the largest class representable by this model, and are a proper superclass of the networks implementable with the infinity fair merge primitive. Finally, we use this characterization to show that infinity fair merge networks and oraclizable networks are proper subclasses of the networks with Egli-Milner monotone input-output relations.

The problem of finding fully abstract semantic models for nondeterministic dataflow networks is discussed. The author presents a result indicating that there exist nondeterministic networks using only bounded choice for which the input-output relation is not compositional. It is shown that the trace semantics is fully abstract for all nondeterministic as well as deterministic networks.>