Reactivity on the Web

Reactivity, the ability to detect simple and composite events and respond in a timely manner, is an essential requirement in many present-day information systems. With the emergence of new, dynamic Web applications, reactivity on the Web is receiving increasing attention. Reactive Web-based systems need to detect and react not only to simple events but also to complex, real-life situations. This paper introduces XChange, a language for programming reactive behaviour on the Web, emphasising the querying of event data and detection of composite events

Processing Queries in a Large Peer-to-Peer System

Abstract. While current search engines seem to easily handle the size of the data available on the Internet, they cannot provide fresh results. The most up-to-date data always resides on the data sources. Efficiently interconnecting data providers, however, is not an easy problem. Peer-to-peer computing is the latest technology to address this problem. However, efficient query processing in peer-to-peer networks remains an open research area. In this paper, we present a performance study of a system that facilitates efficient searches of large numbers of independent data providers on the Internet. In our scenario, each data provider becomes an autonomous node in a large peer-to-peer system. Using small indices on each node, we can efficiently direct queries submitted on any node to the relevant sources. Experiments with a large peer-to-peer network demonstrate the feasibility of our approach.

Creating a Representation of Items and Version that Support Efficient Evaluation of the Transaction-Time Axis in XML-Based Databases

This project was developed to create a platform for implementing the features and query support provided by the transaction time axis (tt-axis). The basis for this platform is a new numbering plan called item version timestamp level numbering (IVTLN), and it extends an existing numbering plan, namely, dewey level numbering (DLN), by including version and timestamp information. Thus, the transaction time axis provides a temporal perspective for XML nodes in addition to non-temporal axes like the ancestor and descendant axes. This project provides an efficient, extensible, and comprehensible platform for the implementation of the new numbering plan and the services provided by the transaction time axis

Monitoring XML Data on the Web

We consider the monitoring of a flow of incoming documents. More precisely, we present here the monitoring used in a very large warehouse built from XML documents found on the web. The flow of documents consists in XML pages (that are warehoused) and HTML pages (that are not). Our contributions are the following: ffl a subscription language which specifies the monitoring of pages when fetched, the periodical evaluation of continuous queries and the production of XML reports. ffl the description of the architecture of the system we implemented that makes it possible to monitor a flow of millions of pages per day with millions of subscriptions on a single PC, and scales up by using more machines. ffl a new algorithm for processing alerts that can be used in a wider context. We suppor