Collaborative tagging as a tripartite network

We describe online collaborative communities by tripartite networks, the nodes being persons, items and tags. We introduce projection methods in order to uncover the structures of the networks, i.e. communities of users, genre families... To do so, we focus on the correlations between the nodes, depending on their profiles, and use percolation techniques that consist in removing less correlated links and observing the shaping of disconnected islands. The structuring of the network is visualised by using a tree representation. The notion of diversity in the system is also discussed

Comparing the hierarchy of author given tags and repository given tags in a large document archive

Folksonomies - large databases arising from collaborative tagging of items by independent users - are becoming an increasingly important way of categorizing information. In these systems users can tag items with free words, resulting in a tripartite item-tag-user network. Although there are no prescribed relations between tags, the way users think about the different categories presumably has some built in hierarchy, in which more special concepts are descendants of some more general categories. Several applications would benefit from the knowledge of this hierarchy. Here we apply a recent method to check the differences and similarities of hierarchies resulting from tags given by independent individuals and from tags given by a centrally managed repository system. The results from out method showed substantial differences between the lower part of the hierarchies, and in contrast, a relatively high similarity at the top of the hierarchies.Comment: 10 page

Analyzing Tag Semantics Across Collaborative Tagging Systems

The objective of our group was to exploit state-of-the-art Information Retrieval methods for finding associations and dependencies between tags, capturing and representing differences in tagging behavior and vocabulary of various folksonomies, with the overall aim to better understand the semantics of tags and the tagging process. Therefore we analyze the semantic content of tags in the Flickr and Delicious folksonomies. We find that: tag context similarity leads to meaningful results in Flickr, despite its narrow folksonomy character; the comparison of tags across Flickr and Delicious shows little semantic overlap, being tags in Flickr associated more to visual aspects rather than technological as it seems to be in Delicious; there are regions in the tag-tag space, provided with the cosine similarity metric, that are characterized by high density; the order of tags inside a post has a semantic relevance

Physics results from BABAR and prospects

The BABAR experiment has been taking data since about one year. Physics results, complementary to those described by G.Sciolla elsewhere in these Proceedings, are presented: various measurements of the neutral and charged B mesons lifetimes, the B^0 mixing frequency, the mistag fractions, and the B --> D_s^(*) X and B^0 --> D_s^(*)+ D^* branching ratios. Some prospects for the close future are shown. All the numbers given here are preliminary.Comment: 12 pages, 12 postscript figures, contributed proceedings of the International Conference On CP Violation Physics, 9/18-22/2000, Ferrara, Ital

b Physics

A summary of the most recent and important measurements in b physics is presented. The production of beauty particles in Z decays, b quark couplings, lifetimes, B0-B0bar oscillations, semileptonic b decays and studies of the number of charm quarks produced in b decays are reviewed. Extraction of the Cabibbo-Kobayashi-Maskawa (CKM) matrix elements |V_{td}|, |V_{cb}|, |V_{ub}| and implication for |V_{ts}| are discussed.Comment: 24 pages, 2 figures, Second Latin American Symposium on High Energy Physics, San Juan, Puerto Rico, April 199