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  • × author_ss:"Spero, S."
  1. Spero, S.: LCSH is to thesaurus as doorbell is to mammal : visualizing structural problems in the Library of Congress Subject Headings (2008) 0.17
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    Abstract
    The Library of Congress Subject Headings (LCSH) has been developed over the course of more than a century, predating the semantic web by some time. Until the 1986, the only concept-toconcept relationship available was an undifferentiated "See Also" reference, which was used for both associative (RT) and hierarchical (BT/NT) connections. In that year, in preparation for the first release of the headings in machine readable MARC Authorities form, an attempt was made to automatically convert these "See Also" links into the standardized thesaural relations. Unfortunately, the rule used to determine the type of reference to generate relied on the presence of symmetric links to detect associatively related terms; "See Also" references that were only present in one of the related terms were assumed to be hierarchical. This left the process vulnerable to inconsistent use of references in the pre-conversion data, with a marked bias towards promoting relationships to hierarchical status. The Library of Congress was aware that the results of the conversion contained many inconsistencies, and intended to validate and correct the results over the course of time. Unfortunately, twenty years later, less than 40% of the converted records have been evaluated. The converted records, being the earliest encountered during the Library's cataloging activities, represent the most basic concepts within LCSH; errors in the syndetic structure for these records affect far more subordinate concepts than those nearer the periphery. Worse, a policy of patterning new headings after pre-existing ones leads to structural errors arising from the conversion process being replicated in these newer headings, perpetuating and exacerbating the errors. As the LCSH prepares for its second great conversion, from MARC to SKOS, it is critical to address these structural problems. As part of the work on converting the headings into SKOS, I have experimented with different visualizations of the tangled web of broader terms embedded in LCSH. This poster illustrates several of these renderings, shows how they can help users to judge which relationships might not be correct, and shows just exactly how Doorbells and Mammals are related.
  2. Spero, S.: LCSH is to thesaurus as doorbell is to mammal (2008) 0.02
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    Content
    "When you look at the Library of Congress Subject headings as individual entries it's almost impossible to understand just how confused much of the hierarchical reference structure has become. I've written some code to generate graphical representations for the Broader Terms of entries in the LCSH. The starting term appears at the bottom of the graph; according to the rules, this term is a specialization of every other term on the graph. Top level terms are highlighted using double circles. Layout and rendering is courtesy of the wonderful graphviz (AT&T Research). I have generated dot files for all entries in the LCSH; I need to set up an dynamic renderer so they can be viewed online, but a p7zip archive raw dot is available here. (5M compressed, 672M uncompressed) Lets see what the LCSH has to tell us about Doorbells. Doorbells are a Social science. Doorbells are Souls. Doorbells are even Ontologies - which would explain why Protege keeps beeping at me. But most of all, Doorbells are mammals. Obviously this conclusion is absurd. Everyone knows that doorbells aren't hairy. But where are the errors that lead us to this mistaken conclusion, and how can we start to correct them? That's the subject of tomorrow's post."

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