Following up on our earlier post respecting Library of Congress Subject Headings (LCSH) marked up in SKOS [URL corrected 10 August 2011], this post suggests the implications of LCSH in SKOS for free or low-cost digital law libraries and aggregators of metadata harvested from such libraries.
In a recent discussion of Tom Bruce’s very interesting post respecting the requirements of a public legal information system, subject indexing of primary and secondary legal resources was identified as a necessary feature of a digital law library. One marked difference between sophisticated commercial computer-assisted legal research (CALR) services, such as Westlaw and Lexis.com, on the one hand; and free or low-cost CALR services, such as those furnished by the legal information institutes (LIIs) or other providers, such as those listed on Georgetown Law Library’s Free & Low-Cost Legal Research page, or those listed on our digital law libraries page, on the other hand; is that the sophisticated commercial services provide high-quality subject indexing to primary law, featuring controlled subject vocabularies, such as Lexis.com’s Legal Topics and West’s Key Number System. Moreover, Westlaw and Lexis.com appear to have rendered their controlled subject vocabularies machine-readable, so as to enable certain kinds of automated subject search and retrieval of primary law. Machine-readable controlled vocabulary subject indexing substantially improves recall and precision and results in substantial time savings to the user, and so appears to be a critical aspect of the value added to legal information by the sophisticated CALR vendors.
The release of LCSH in SKOS raises the prospect that the LIIs and other free or low-cost CALR services can similarly enhance the value of their primary and secondary law collections. LCSH in SKOS is a public-domain, machine-readable, controlled subject vocabulary containing a very rich set of thousands of legal terms pertaining to a diversity of legal traditions and systems (including common law & civil law systems and the system of public international law) and thousands of cross references to unauthorized and related terms. When matched with automated subject indexing tools (see, e.g., here and here) LCSH in SKOS could allow free or low-cost digital law libraries to provide sophisticated subject access to their collections at an affordable expense. The free services could even collaborate on such indexing, and so realize further efficiencies. Moreover, the same controlled vocabulary can be used for primary and for secondary legal resources, enabling cross-database searching and providing substantial time and cost savings to users. Further, LCSH in SKOS can be linked to controlled subject vocabularies or ontologies in other languages (e.g., perhaps eventually through the Virtual International Authority File), to facilitate multi-lingual controlled vocabulary subject search and retrieval in digital law libraries.
In addition, LCSH in SKOS could enhance subject access to legal information across multiple services. To the extent that LCSH in SKOS is integrated into descriptive metadata for individual legal resources (for an interesting recent primary-law example, see MODS files for the Federal Register on FEDSYS, click on “More”), in OAI-PMH compliant databases, and such metadata is harvested and made publicly available, LCSH in SKOS could facilitate controlled-vocabulary subject retrieval of legal resources across multiple digital law libraries.
Public availability of LCSH in SKOS thus potentially represents a major breakthrough in improved intellectual access to law for users of free or low-cost digital law libraries.