I don’t think that folksonomies will supplant formal subject headings and taxonomies. There’s plenty of room to experiment with the interplay between folksonomic and taxonomic approaches. Indeed, how can one combine some of the simplicity of tagging with the careful structures of formal classification schemes? In this section, I show a specific example to highlight some of the relevant challenges.

Let’s return to an example I first used in Chapter 1, the book Czesław Miłosz’s New and Collected Poems 1931–2001, specifically the hardcover edition with the ISBN-10 of 006019667X. You can search for the book at the Library of Congress here to learn how the Library of Congress has formally classified the book and its author:

http://catalog.loc.gov/cgi-bin/Pwebrecon.cgi?v3=1&DB=local&CMD=kisn+006019667X&CNT=10+records+per+page

The book is assigned to the Library of Congress Subject Heading (LCSH) Miłosz, Czesław Translations into English:

http://catalog.loc.gov/cgi-bin/Pwebrecon.cgi?SC=Subject&SA=Mi%C5%82osz%2C%20Czes%C5%82aw%20Translations%20into%20English

Through this subject heading, which you can access through its corresponding URL, you can get all the books that are classified in the same group. In this specific case, you can reliably find a list of many, if not all, of the English translations of Miłosz’s poetry published in the United States.

Why does this matter? By using the LCSH as a category, you get to leverage the careful and reliable work that the Library of Congress has done in classifying books. Just because you use tags doesn’t mean you have to ignore formal classifications.

The LCSH is not the only formal classification scheme around for books. If you look the same book up at the Online Computer Library Center (OCLC) WorldCat.org site, like so:

http://worldcatlibraries.org/wcpa/isbn/006019667X

you will find the look listed under the subject of Miłosz, Czesław:

http://worldcatlibraries.org/search?q=su%3AMi%C5%82osz%2C+Czes%C5%82aw

The subject headers used by OCLC are based on its FAST project, which aims to simplify yet be upward compatible with LCSH:

http://www.oclc.org/research/projects/fast/

To see a sophisticated example of how tags can be effectively combined with formal classification, let’s look at OCLC, where you can get a different subject category for the same book:

http://worldcatlibraries.org/search?q=su%3AMi%C5%82osz%2C+Czes%C5%82aw

You can feed an ISBN to LibraryThing, a social book-­cataloging site, with this:

http://www.librarything.com/isbn/{isbn}

which will redirect to a URL with a work-id tag (different editions of a book, which can have different ISBNs, are collected under the same work-id):

http://www.librarything.com/work/{librarything-work-id}

Using our example, the following URL:

http://www.librarything.com/isbn/006019667X

redirects to the following:

http://www.librarything.com/work/161671

where you see tags that users of LibraryThing have applied to the book. At the same time, you can find LibraryThing lists here:

http://www.librarything.com/work-info/{librarything-work-id}

For example:

http://www.librarything.com/work-info/161671

The following is how the book has been formally classified (including such metadata as the Library of Congress Call Number and the Dewey Decimal classification) along with the LCSH:

http://www.librarything.com/subject.php?subject=Mi%B1osz%2C+Czes%B1aw%09Translations+into+English

	Caution
	There is an error in character encoding in LibraryThing that causes Miłosz, Czesław to be incorrectly displayed.[68]