Nature.com is now adding XMP packets into its PDFs. XMP is Adobe's Extensible Metadata Platform - a framework for embedding metadata into arbitrary binary files. Basically, these are simple XML documents (conforming to a profile of RDF/XML) which carry metadata about the work published in the PDF.

A number of tools exist to extract XMP packets. One such easy-to-use, cross-platform tool is ExifTool:

    http://www.sno.phy.queensu.ca/~phil/exiftool/

ExifTool is a platform-independent Perl library plus a command-line application and is available both as a standalone Windows executable (no Perl required) and a Macintosh OS X package.

An XMP Primer (PDF) providing a simple introduction to metadata and to XMP is available from the XMP-Open industry initiative:

http://www.xmp-open.org/

General information on XMP can be found at the Adobe product page:

http://www.adobe.com/products/xmp/

Please address any specific queries about use of the nature.com XMP interface to interfaces@nature.com.