ONIX is an international metadata standard for communicating book product information electronically between publishers, distributors, retailers, and other entities involved in the book supply chain. ONIX allows global communication of book information regardless of language or technical infrastructure. ONIX 3.0 updated the standard to better reflect the global digital book market by improving how digital formats, pricing, and multilingual data can be described. Thema is a new global subject category classification system that aims to help the international book trade clearly communicate subject information for physical and digital products using a common standard.