Page web | EPFL Graph Search

alt=|vignette|Une page web de Wikipédia. La page web, ou page Web, est l'unité de consultation du World Wide Web. Ce terme a une signification pratique ; il n'a pas de définition technique formelle. Les pages web sont conçues pour être consultées avec un navigateur web. Elles sont identifiées par une adresse web. Techniquement, une page web est généralement constituée d'un document rédigé en Hypertext Markup Language (HTML) pour la structure de base, d', de feuilles de style en cascade (CSS) pour la mise en page, et de JavaScript pour la programmation informatique des fonctionnalités plus avancées. Terminologie Depuis 1999, la Commission d'enrichissement de la langue française recommande le terme page sur la toile. Cette recommandation n'a guère été suivie. Utilisation Identification et accès L'accès à une page est donné par son adresse web, que l'on peut :

entrer soi-même dans la barre d'adresse d'un navigateur web ;
ou activer

Type-based event dissemination

Sébastien Bähni

With the explosion of broadband Internet connections in the late 80s, new types of applications, called distributed applications, came to light. These applications typically seek to provide a user with remote services that appear to that user as if they were local. For instance, when a user browses the Internet, web pages are downloaded from different servers and are displayed on the screen of the client's computer as if they were directly available on the computer itself. Typically one distinguishes two kinds of actors in such applications: clients, searching for information, and servers, providing the information. Furthermore, there are generally two models of interaction according to which these actors exchange information. In the first model, the client requests specific information and waits until the server replies to it. In the second model, the client registers its interests in some information with a set of servers and is notified when new information is available. Both models have their advantages and disadvantages but the second has obvious asynchrony benefits in a large-scale system in which it is very difficult to know the time taken to answer a request. The second model is usually encapsulated within the celebrated publish/subscribe abstraction. According to this abstraction, clients are either subscribers which express interest in specific information, or publishers which create and send pieces of information usually transmitted in the form of events (e.g., as HTML pages or plain data). The subscriber does not need to know a publisher or to be on-line with it to receive its published events. These properties are sometimes refer to as space and time decoupling respectively. Newsgroups are the most well known example of publish/subscribe system. While indeed appealing, the publish/subscribe abstraction is not easy to implement effectively. There are at least two challenging issues: (1) the representation of the events and (2) their dissemination on a large-scale or in a mobile environment. Events are usually transferred as XML messages or byte arrays. The system must therefore transform events into pieces of software implemented in its underlying language (e.g., Java, C#) before handling them. In addition, the reliable dissemination on a large-scale or in a mobile environment is not trivial, especially as in practice it is necessary to minimize the number of duplicates and parasite events (i.e., events of no interest) to save bandwidth and processing power. We focus in this thesis on devising and implementing algorithms which address the above two issues in publish/subscribe systems implemented in object-oriented languages (e.g., Java, C#) and such that the events that are transferred between the different actors correspond to serialized objects. These systems are also called type-based publish/subscribe systems. We first present techniques to detect events of interest and throw away parasite events. We show that these techniques are of major use for reliably disseminating events either on a large-scale or in a mobile environment without flooding the network. Finally, we illustrate type interoperable rules that let instances of two different types, but still representing the same entity, to be used indistinguishably. Together with the algorithms, we exhibit implementation prototypes and performance measures conducted over them.

EPFL2006

Understanding the Web

Eda Baykan

The World Wide Web is one of the most widely used information resources. Understanding the web better will enable us to benefit more of it. In this thesis we develop techniques to learn the properties of the web pages like language and topic using only the URLs of web pages. Furthermore we make a comparison and evaluation of web page sampling algorithms to learn about the web properties like content length, top level domain and outdegree distribution. In the first part of this thesis, we develop high performance classifiers for web page language classification using only the URL of web pages. We make a comprehensive study of features and algorithms and test the performance of our classifiers on various real data sets. For language classification the quality of our URL-based classifiers rival the quality of classifiers based on content. Language classification from URL is useful when the content of the web page is not available and when the classification speed is important. Language classifiers based on URLs can be used by crawlers of general and language specific search engines to avoid bandwidth waste. In the second part of this thesis, we investigate whether web page topic classification can be done only with URL. We explore this problem in various dimensions like experimenting with different algorithms, features, data sets and topics. URL-based topic classification is useful when the content of the web page is not available or the content is hidden in images. Topic classifiers based on URLs can be used to filter information and in applications like topic focused crawlers. Although content based topic classifiers give better performances, our URL-based topic classifiers work reasonably well and can be used as a signal to improve the performance of content based classifiers. In the third part of this thesis, we compare the state of art web page sampling algorithms and analyze the samples returned by these algorithms using the web properties like content length, top level domain and outdegree distribution. We discuss the strengths and weaknesses of each algorithm and propose improvements based on experimental results. The sampling algorithms we run on the web are influenced by the structure of the web. We investigate the relationship between the properties of the web and the structure of it. A uniform random sample of the web would be quite useful to learn about the composition and development of the web as it is not possible to download all the web pages to determine the properties of the web.

EPFL2009

A Comparison of Techniques for Sampling Web Pages

Eda Baykan, Monika Henzinger

As the World Wide Web is growing rapidly, it is getting increasingly challenging to gather representative information about it. Instead of crawling the web exhaustively one has to resort to other techniques like sampling to determine the properties of the web. A uniform random sample of the web would be useful to determine the percentage of web pages in a specific language, on a topic or in a top level domain. Unfortunately, no approach has been shown to sample the web pages in an unbiased way. Three promising web sampling algorithms are based on random walks. They each have been evaluated individually, but making a comparison on different data sets is not possible. We directly compare these algorithms in this paper. We performed three random walks on the web under the same conditions and analyzed their outcomes in detail. We discuss the strengths and the weaknesses of each algorithm and propose improvements based on experimental results.

2009