The subject of this paper is the creation of knowledge bases by enumerating and organizing all web occurrences of certain subgraphs. We focus on subgraphs that are signatures of web phenomena such as tightly-focused topic communities, webrings, taxonomy trees, keiretsus, etc. For instance, the signature of a webring is a central page with bidirectional links to a number of other pages. We develop novel algorithms for such enumeration problems. A key technical contribution is the development of a model for the evolution of the web graph, based on experimental observations derived from a snapshot of the web. We argue that our algorithms run efficiently in this model, and use the model to explain some statistical phenomena on the web that emerged during our experiments. Finally, we describe the design and implementation of Campfire, a knowledge base of over one hundred thousand web communities. 1 Overview The subject of this paper is the creation of knowledge bases by ...

In this paper we review studies of the growth of the Internet and technologies that are useful for information search and retrieval on the Web. We present data on the Internet from several different sources, e.g., current as well as projected number of users, hosts, and Web sites. Although numerical figures vary, overall trends cited

This article is extracted and adapted from Ben Shneiderman's newly revised and recently published book, Designing the User Interface: Strategies for Effective Human---Computer Interaction (Third Edition), Addison Wesley Longman, Copyright 1998, with the permission of the publisher.

We develop a technique we call spectral filtering, for discovering high-quality topical resources in hyperlinked corpora. Through relevance and quality judgements collected from 37 users, we show that, over 26 topics, spectral filtering usually finds web pages that are rated better than those returned by the hand-compiled Yahoo! resource list, and by the Altavista search engine.

The World-Wide Web is becoming an invaluable source for the information needs of many users. However, current browsers are still primitive, in that they do not support many of the navigation needs of users, as indicated by user studies. They do not provide an overview and a sense of location in the information structure being browsed. Also they do not facilitate organization and filtering of information nor aid users in accessing already visited pages without high cognitive demands. In this paper, a new browsing interface is proposed with multiple hierarchical windows and efficient multiple window operations. It provides a flexible environment where users can quickly organize, filter, and restructure the information on the screen as they reformulate their goals. Overviews can give the user a sense of location in the browsing history as well as provide fast access to a hierarchy of pages.

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Network-accessible multimedia databases, repositories, and libraries are proliferating at a rapid rate. A crucial problem for these repositories remains timely and appropriate document access. In this paper, we borrow a model from psychological research on human memory, which has long studied retrieval of memory items based on frequency and recency rates of past item occurrences. Specifically, the model uses frequency and recency rates of prior document accesses to predict future document requests. The model is illustrated by analyzing the log file of document accesses to the Georgia Institute of Technology World-Wide Web (WWW) database, a large multimedia repository exhibiting high access rates. Results show that the model predicts document access rates with a reliable degree of accuracy. We describe extensions to the basic approach that combine the recency and frequency analyses, and incorporate repository structure and document type. These results have implications for the formulati...

Multimedia repositories, libraries, and databases offer the potential for providing students with access to a wide variety of interconnected information resources. However, in order to realize this potential, multimedia systems should provide access to information and activities that support effective knowledge construction and learning by students. This article proposes a theoretical framework for organizing information and activities in educational hypermedia systems. We show that such systems should not be characterized primarily in terms of the kinds of physical media types that can be accessed; instead, the important aspect is the content that can be represented within a physical media, rather than the physical media itself. We propose a theory of "cognitive media types" based on the inferential and learning processes of human users. The theory highlights specific media characteristics that facilitate specific problem solving actions, which in turn are enabled by specific kinds of...

We provide a framework that allows one to study structural properties of hypertext in connection with formal language theory. We model hypertext as a transformation device (an atransducer) that transforms a link-following into a sequence of matched pairs: basic linkable units. Then, we address the following questions: What can hypertext do? What structure is formed when a link-following is done? What structure is built when a virtual document is constructed? We show that the set of all link-followingsin hypertext is a regular set. Then, the set of all possible outputs of link-followings is shown to be context-free, which means that constructing virtual documents is essentially same as generating words of a contextfree language. KEYWORDS: Hypertext structure, Dexter model, regular set, context-free language, Hypertext models, link-following, atransducer, virtual document. INTRODUCTION Structure information in hypertext is important in many ways. One can make use of underlying hyperte...

One of the main unsolved problems confronting Hypertext is the navigation problem, namely the problem of having to know where you are in the database graph representing the structure of a Hypertext database, and knowing how to get to some other place you are searching for in the database graph. In order to tackle this problem we introduce a formal model for Hypertext. In this model a Hypertext database consists of an information repository, which stores the contents of the database in the form of pages, and a reachability relation which is a directed graph describing the structure of the database. The notion of a trail, which is a path in the database graph describing some logical association amongst the pages in the trail, is central to our model. We define a Hypertext query language for our model based on a subset of propositional linear temporal logic, which we claim to be a natural formalism as a basis for establishing navigation semantics for Hypertext. The output of a trail query in this language is the set (which may be infinite) of all trails that satisfy the query. We show that there is a strong connection between the output of a trail query and finite automata in the sense that, given a Hypertext database and a trail query, we can construct a finite automaton representing the output of the query, which accepts a star-free regular language. We show that the construction of the finite automaton can be done in time exponential in the number of conjunctions, between the subformulae of the trail query, plus one. Given a Hypertext database and a trail query, the problem of deciding whether there exists a trail in the database that satisfies the trail query is referred to as the model checking problem. We show that, although this problem is NP-complete for differ...