Extracting Hymns from Hymnological Texts

I have several books which consist "primarily" of hymnological information: biographies, analyses, etc., but which include some complete hymn texts and also some quoted fragments of hymns: e.g., "Sweet Singers of Wales" and "Christian Singers of Germany" already at CCEL. Now, these books are intended partly as original publication of new translations, and as such provide "authority records" for those hymns. So I'd like to see the complete hymns automatically extracted and added to the Hymnary.

But ... I've marked up the hymn fragments in tags to keep the XML validator happy ( and tags not allowed in other contexts).

Is there a recommended way for a hymn-extractor to distinguish between tags around versified fragments, or tags around complete extractable hymns?

Some possible ideas (I haven't checked to see which of these are compatible with the ThML DTD:
-- no "n=" attribute for fragments
-- no "title" attribute
-- class="fragment" attribute

As usual, there are a couple of books in the pipeline that will be affected.