The Global Digital Library (GDL) project has defined a common set of metadata based on the Learning Resources Metadata Initiative (LRMI) Specification Version 1.1. This will ensure quality and allow for the GDL platform to present resources with a consistent set of metadata.
For more information, see (on the Internet):
GDL metadata and file formats for resources 1.0
Use the Book Metadata dialog box
https://en.wikipedia.org/wiki/Learning_Resource_Metadata_Initiative