The short version of the functions available:
- ISBN: get checkdigit, validate, convert isbn10 to/from isbn13, normalize (to 13-digit)
- ISSN: get checkdigit, validate, normalize
- LCCN: validate, normalize
Validation of LCCNs doesn’t involve a checkdigit; I basically just normalize whatever is sent in and then see if the result is syntactically valid.
My plan in my Copious Free Time is to do a Java version of these as well and then stick them into a new-style Solr v.3 filter so I (and, by extension, you, if you’re interested) can have Solr do normalization during both index and search time.