Distributed Information and Control in a Concurrent Hypermedia-Oriented Architecture

Abstract

The market for parallel and distributed computing systems keeps growing. Technological advances in processor power, networking, telecommunication and multimedia are stimulating the development of applications requiring parallel and distributed computing. An important research problem in this area is the need to find a robust bridge between the decentralisation of knowledge sources in information-based systems and the distribution of computational power. Consequently, the attention of the research community has been directed towards high-level, concurrent, distributed programming. This work proposes a new hypermedia framework based on the metaphor of the actor model. The storage and run-time layers are represented entirely as communities of independent actors that cooperate in order to accomplish common goals, such as version management or user adaptivity. These goals involve fundamental and complex hypermedia issues, which, thanks to the distribution of tasks, are treated in an efficient and simple way. Keywords: Distributed hypermedia design, open hypermedia systems, configuration management, adaptive hypermedia systems, object-oriented concurrent design, actorbased models. Int. J. Soft. Eng. Knowl. Eng. 2000.10:345-369. Downloaded from www.worldscientific.com by MONASH UNIVERSITY on 02/05/15. For personal use only. Distributed Information and Control in a Concurrent Hypermedia-Oriented Architecture 347 actor, myactor, according to this form: ( Def myactor {inherit-from-this-class} (acquaintance list) [communication list] )An actor is described by specifying three elements: its superclass, its data part and its script part, respectively put between braces, parentheses and brackets. In particular, the communication list is a sequence of scripts which can be executed by myactor. The communication between a sender and one or more receivers is accomplished by the "send" command types:• send allows an actor to send a point-to-point message;• send-multicast allows an actor to send multicasting messages on the net;• send-now-multicast is similar to the previous send-multicast, but it requires an "acknowledge" message from the receiver actors.A general form of the send construct is the following:send − type (script-name argument-list) to destination-list where send − type . . . to is one of the send commands; script-name argument-list determines the script (with its arguments, if any) that the destination actors trigger once they have received the message, while destination-list, introduced by the keyword to , identifies the actor(s) to which the message is addressed. The Storage Layer ModelThe storage layer model constitutes the structure of the hypermedia as provided by its author. The main purpose of this layer is to maintain the persistent objects, the collection of which defines the hypermedia in terms of dynamic internal mechanisms. The storage layer is organised in two levels:• The first level, named Structural Level, contains atomic nodes (named Hy-pActors) and links (named HypLinks). • The second level is named...

Synchronizing Interactive Web Documents With Fd-Java Constraints

“…The authoring system is based on different software components that help the designer in the specification of the architecture. Our design approach follows previous experiences dedicated to the design of open hypermedia authoring architectures (see [26]). The software components that perform the constraint flow management are enclosed in the "Constraint Interaction Technique Libraries" (CITL).…”

A fuzzy approach to adaptive hypermedia

“…When the project HyDe (Hypermedia Distributed Design) [9] started in the beginning of 90's we were essentially concerned with the study, realisation and experimentation of a set of new tools for designing hypermedia authoring systems. We decided to adopt as basic platform the language HyperCLAS, an extension of CLOS (Common Lisp Object System) [?I towards concurrent computing.…”