"What can we do TODAY to get ready for linked data?"It's not really a hard question, because, at least in my mind, there is an obvious starting point: identifiers. We can begin today to connect the textual data in our bibliographic records with identifiers for the same thing or concept.
What identifiers exist? Thanks to the Library of Congress we have identifiers for all of our authority controlled elements: names and subjects. (And if you are outside of the US, look to your national library for their work in this area, or connect to the Virtual International Authority File where you can.) LoC also provides identifiers for a number of the controlled lists used in MARC21 data.
The linked data standards require that identifiers be in the form of an HTTP-based URI. What this means is that your identifier looks like a URL. The identifier for me in the LC name authority file is:
control subfield was added to MARC21 for identifiers ($0), that subfield requires the identifier to be in a MARC21-specific format:
The control number or identifier is preceded by the appropriate MARC Organization code (for a related authority record) or the Standard Identifier source code (for a standard identifier scheme), enclosed in parentheses.The example in the MARC21 documentation is:
100 1#$aBach, Johann Sebastian.$4aut$0(DE-101c)310008891Modified to use LC name authorities that would be:
100 1#$aBach, Johann Sebastian,$d1685-1750$0(LoC)n79021425The contents of the $0 therefore is not a linked data identifier even in those instances where we have a proper linked data identifier for the name. Catch-21. I therefore suggest that, as an act of Catch-21 disobedience, we all declare that we will ignore the absurdity of having recently added an anti-linked data identifier subfield to our standard, and use it instead for standard HTTP URIs:
100 1#$aBach, Johann Sebastian,$d1685-1750$0http://id.loc.gov/authorities/names/n79021425Once we've gotten over this hurdle, we can begin to fill in identifiers for authority-controlled elements. Obviously we won't be doing this by hand, one record at a time. This should be part of a normal authority update service, or it may be feasible within systems that store and link national authority data to bibliographic records.
We should also insist that cataloging services that use the national authority files begin to include these subfields in bibliographic data as it is created/downloaded.
Note that because the linked data standard identifiers are HTTP URIs, aka URLs, by including these identifiers in your bibliographic data you have already created a link -- a link to the web page for that person or subject, and a link to a machine-readable form of the authority data in a variety of formats (MARCXML, JSON, RDF, and more). In the LC identifier service, the name authority data includes a link to the VIAF identifier for the person; the VIAF identifier for some persons is included in the Wikipedia page about the person; the Wikipedia identifier links you to DBpedia and the DBpedia identifier is used by Freebase ...
That's how it all gets started, with one identifier that becomes a kind of identifier snowball rolling down hill, collecting more and more links as it goes along.
Pretty easy, eh?