Jeff Beall reposts some of the discussion on the MODS mailing list on the recently published draft of MADS/RDF. Beall wonders if the proposal, and the initial comments indicate that the entire semantic web effort is doomed. This may be an over-reaction.
I spent some time working on a formal analysis of the semantics of pre-combined/subdivided subject headings, and how they could be added in a downwards compatible way to SKOS. I had hoped to discuss the topic at the DC VOCAMP held at The Library immediately after ISWC 2009, but there was no-one at the camp who was interested in library vocabularies, I let the matter drop.
Since support for pre-combined headings are one of the major design goals of MADS/RDF, I have been looking quite closely at the initial draft. I am not yet ready to publish detailed results, but I wanted to take this chance to make a few quick notes on the initial draft.
There is a quick change that could make it easier for others to evaluate the proposed ontology. Currently, the URI/IRI of the ontology is “http://id.loc.gov/ontologies/mads/2010/11″. At the moment does not resolve as a URL. Also, the name is slightly different from current usual practice. Ontology URIs are typically of the form …/<Year>/<Month>/<Name>; the MADS IRI is in the form …/<Name>/<Year>/<Month>. This encourages some common tools, such as Protege, to abbreviate the ontology name as “11″.
- The SKOS mappings are imported as part of the reference ontology; however due to problems in naming, this may not show up correctly. It might be better to include the axioms in the mapping file directly in the main ontology.
- The SKOS mappings are incomplete; it is possible that concentrating on narrowing the differences between SKOS and Standard(NISO Z39.19)/Library KOS semantics would give an end result that should be more useful for use by The Library.
- The current draft was created without support from an ontologist or owl expert. There are several problems in the modeling that result from this lack of resourcing. For example, there are several places where a constraint or restriction is given in a comment that could readily have been represented in OWL, and many properties are not fully or properly specified. There is a big difference between the ontology design and schema design, and without support resources, it is easy to fall in to some common anti-patterns.
- The current draft was created without ready access to Subject Matter Experts (SMEs) in the Cataloging COI. As a result, the ontology may not adequately represent the problem domain, and may make it harder to extend so as to support LC rules and policy on subject heading formation. When modeling any complex area, regular interaction with relevant SMEs is essential throughout the process, both for knowledge elicitation and model validation. Early, regular review of the ongoing work by MODS/MADS Editorial Committee may be helpful.
- The current draft does not define the semantics of pre-combined headings; there are different possible interpretations, but none are discussed, and some inferences appear to be common across all readings.
- Given known data errors in the syndetic structure of LCSH (see e.g. LCSH is to Thesaurus as Doorbell is to Mammal), it may better to devote resources to correcting these issues before deepening the semantics of exposed Linked Data. This would make the LC vocabularies more reuseable in the web of data, as recommended in the Deanna Marcum’s ”Response to: On the record: Report of the Library of Congress Working Group On The Future of Bibliographic Control“.
 Following Soergel, I prefer this term to “Pre-coordinated”
 I also worked on relating the to the implied ontologies inferable from Knowledge Organization Systems that used sub-types of BT relationship (BTG, etc) that are part of the international standards, and which were originally included in SKOS, but which were moved to an extension , then finally dropped and relegated to examples in the published recommendation.