ONIX (ONline Information eXchange) currently refers to any of three XML standard metadata formats developed by EDItEUR for use primarily within the book trade. ONIX was originally a single standard for capturing and communicating bibliographic data relating to books. That standard is now referred to as ONIX for Books and has been expanded to include better support for eBooks. A second ONIX family of standard messages, ONIX for Serials has been added to capture metadata pertaining to serialised publications. There is also a third standard, ONIX for Publications Licenses (ONIX-PL), designed to handle the licenses under which libraries and other institutions use digital resources.