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Welcome to the 19th ACM Conference on Hypertext and Hypermedia -- Hypertext 2008. One of the great joys of the Hypertext conference series has always been the diversity of the topics that the conference encompasses. Regular attendees have always known and valued this diversity, but the conference steering committee have been aware that it can be confusing to newcomers, and at times difficult for reviewers who have to decide whether a paper is 'in-scope' for the conference. This year we have refined the approach that we began last year, whereby we have had four separate tracks, each with their own chairs and committees; these committees have been responsible for selecting and briefing their reviewers and advertising the call for papers into their communities. We believe that this approach has made the conference more accessible to newcomers, and this has been reflected in the increased quantity and quality of papers submitted.

The conference theme this year is "linking people and places" and celebrates the power and importance of the link, in its widest sense.

The first track, Information Linking and Organization, specifically targets the formal study of scholarly, structural, sculptural, spatial, open, dynamic and adaptive or any other type of hypertext (or Web-based Information System). In this track, researchers discuss models, architecture, interfaces, properties, or theory in general, about hypertext and hypermedia.

The second track, Applications of Hypertext, has been for many years the most difficult for people to scope; it targets descriptions of applications of hypertext, for example in healthcare, cultural heritage, education or industry, where the affordance of the link has in some way enabled a novel application.

The third track, Hypertext, Culture, and Communication, examines the creation and reception of literary machines ranging from literary fiction to creative nonfiction and scholarly argumentation. As hypertext reading and writing become ever more pervasive in society, the rhetoric of links continues to offer frequent surprises and unexpected opportunities. This year's papers integrate fresh insights into spontaneous forms and ephemeral social media with considered reflection on carefully crafted hypermedia.

Social Linking track expands the remit of the Social Hypertext track introduced in 2007. This track focuses on one of the most exciting recent developments in Web science, social annotation, by which users can easily markup other authors' resources via collaborative mechanisms such as tagging, filtering, voting, editing, classification, and rating. These social processes lead to the emergence of many types of links between texts, users, concepts, pages, articles, and media. The social linking track has immediately established itself as the most popular venue for this year's Hypertext technical submissions, covering several aspects of design, analysis, and modeling of information systems driven by social linking. The accepted papers represent a high-quality sample of research covering a broad range of social linking topics, which include the co-evolution of social, information, and semantic networks; formal models of social annotation and its behavioral patterns; link inference from blogs and social networks; applications to search, retrieval, recommendation, navigation, and scalability issues; information-theoretic aspects of socially-induced semantic networks; structure and dynamics of social information networks; and evaluation of mechanisms and interfaces for social linking systems.

This is the third time the Hypertext Conference has been held in Pittsburgh. We are very fortunate, this time, to have excellent keynote presentations from Bernardo Huberman of HP Labs and Prof. Jon Kleinberg of Cornell University, and an excellent technical and social program to look forward to.

In addition to the contributions featured in this volume Hypertext 2008 offered two workshops: ;)

• Web Science: Collaboration and Collective Intelligence organized by Weigang Wang (University of Manchester, UK) and David Millard (University of Southampton, UK)

• Creating out of the Machine: Hypertext, Hypermedia, and Web Artists Explore the Craft organized by Stephen Ersinghaus (Tunxis Community College, Connecticut, USA)