isbn.pl contains a single, simple function which returns a book record from the US Library of Congress based on a single incoming ISBN. It is intended for use in other packages, such as barcode reader drivers, to provide users of those tools with the extensive cataloging metadata librarians have created over the years. It differs from other tools seen so far in that the data returned is in the MARC format, the heavily used, ancient metadata standard originally based on library catalog cards. It thus provides much data in a known syntax via a known query protocol (z39.50, using Zeta), rather than via Web page screen scraping.
