This paper investigates some problems associated with an argument evaluation order that we call "future' order, which is different from both call-by-name and call-by-value. In call-by-future, each formal parameter of a function is bound to a separate process (called a "future") dedicated to the evaluation of the corresponding argument. This mechanism allows the fully parallel evaluation of arguments to a function, and has been shown to augment the expressive power of a language. We discuss an approach to a problem that arises in this context: futures which were thought to be relevant when they were created become irrelevant through being ignored in the body of the expression where they were bound. The problem of irrelevant processes also appears in multiprocessing problem-solving systems which start several processors working on the same problem but with different methods, and return with the solution which finishes first. This parallel method strategy has the drawback that the processes which are investigating the losing methods must be identified, stopped, and reassigned to more useful tasks. The solution we propose is that of garbage collection. We propose that the goal structure of the solution plan be explicitly represented in memory as part of the graph memory (like Lisp's heap) so that a garbage collection algorithm can discover which processes are performing useful work, and which can be recycled for a new task. An incremental algorithm for the unified garbage collection of storage and processes is described.

This paper examines a formal model of how specifications can be constructed from multiple viewpoints and presents some tools to support this approach. The development of specifications is presented as a dialogue in which the viewpoints negotiate, establish responsibilities and cooperatively construct a specification. The model is illustrated by means of some small examples. Keywords: formal specification, distributed artificial intelligence, dialogue, logic, tool support 1 Introduction "Specification-in-the-large", that is the development of requirements specifications for systems of substantial complexity and scale, mirrors "programming-in-thelarge " in raising a variety of difficulties that lie beyond the clerical problems of handling large amounts of information (Cunningham, Finkelstein et al 1985, Finkelstein & Potts 1987). One such difficulty is that of specification from multiple viewpoints (Niskier 1987). Specification-in-the-large is an activity in which there are many particip...

The blackboard architecture has been successfully employed for a number of years and in different application domains. It is taken by many that there is only one possible interpretation of Newell's original blackboard metaphor, namely the one used in the design of HEARSAYII, the first blackboard system. This view is, however, completely false, and we present a new interpretation based on a rationalised reading of the metaphor. The consequence of this is an agent-based architecture which includes a remote, yet globally accessible, database which now records messages and other forms of public information. Experts are now considered to be somewhat more capable than formerly, and they are also considered to have a persistent internal state. Experts, in the new interpretation, are permitted to communicate with other experts without having to post messages on the blackboard. 1 Introduction The blackboard architecture [2, 4, 5, 6, 18] has been successfully used for many years. It has often b...

This paper describes an approach to conceptual analysis and understanding of natural language in whlch linguistic knowledge centers on individual words, and the analysis mechanisms consist of interactions amonR distributed procedural experts representing that knowledge. Each word expert models the process of alagnosing the intended usage of a particular word in context. The Word Expert Parser perform conceptual analysis through the interactions of the individual experts, which ask questions ano exchange information in converging on a single mutually acceptable sentence meaning. The Word Exper theory is advanced as a better cognitive model of natural languaRe understanding than the traditional rule-based approaches. The Word Expert Parser models parts o[ ire theory, and the important issues of control and representation that arise in developing such a model form the basis of the technical discussion. An example from the prototype LISP implementation helps explain the theoretical results presented