The information available on the World Wide Web changes with incredible speed. New information is added and old information is altered. This means that a document which is important to a user accessing the Web may change, move or even disappear altogether. Described here is an autonomous agent, written in Java, which locally archives documents that are deemed important by the user. These locally archived documents are then available-quickly-when needed.

For several years the authors have been part of an effort developing automated techniques for examining the syntax of protocols for the absence of various errors. Recently, we have turned our attention to trying to prove various functional properties of protocols used in ring-topology systems. Ring systems have a number of properties that distinguish them from the more general computer networks towards which our earlier validation work was directed. We report here on the resulting changes in the protocol models and validation techniques, together with extensions used to prove that the protocol being examined has the various desirable functional properties demanded of it.

The existence of a program for automatically examining the syntax of a protocol for the absence of various undesired properties-such as deadlock-raises the question whether the classical `lockups' described in the early packet-switched data network literature could be detected by such a program. The authors answer this question in the affirmative.

The production of error-free protocols or complex process interactions is essential to reliable communications. This paper presents techniques for both the detection of errors in protocols and for prevention of errors in their design. The methods have been used successfully to detect and correct errors in existing protocols. A technique based on a reachability analysis is described which detects errors m a design. This "perturbation technique" has been implemented and has successfully detected inconsistencies or errors in existing protocol designs including both X.21 and X.25. The types of errors handled are state deadlocks, unspecified receptions, nonexecutable interactions, and state smbiguities. These errors are discussed and their effects considered. An interactive design technique is then described that prevents design errors. The technique is based on a set of production rules which guarantee that complete reception capability is provided in the interacting processes. These rules have been implemented in the form of a tracking algorithm that prevents a designer from creating unspecified receptions and nonexecutable interactions and monitors for the presence of state deadlocks and ambiguities.

An inherent capability of packet-switched networks is the speed at which they can be reconfigured; various dynamic or adaptive routing techniques have been conceived to exploit this capability. In this study, existing techniques are described and an "ultra-dynamic" technique, delta routing, is invented. Several promising techniques are then selected for comparison with one another and with a network's ultimate carrying capacity. The goal is to shed light on the questions if and when one should use which kind of adaptive routing. First, a taxonomy of routing strategies is presented. In addition to delta routing, random, proportional, shortest path, and shortest path fixed-for-session duration are selected for comparison and their mechanisms described. The delay and efficiency performance of the five techniques are then compared with one another and with ideal behavior via simulations. These have been carried out concentrating on four very small networks, each with very different characteristics with the intention of gaining insight into the strengths and weaknesses of the various techniques. A ten-node network has also been simulated. The results favor delta routing which is most effective in highly interconnected network enviroments.

When messages are transmitted as a series of possibly noncontiguous packets, an effective priority is introduced which favors short messages. The strength of this effect upon transmission time is investigated and compared with schemes where an additional priority scheme is imposed. It is found that imposing a real priority structure can markedly influence delays when: first, the trunks are relatively heavily loaded, and second, the nodes' incoming traffic arrives over high-speed channels.