Adriano, I am not sure I fully understand your question. Are you asking if the media type registration need to be in the same document as the payload specification. Look in RFC 4855 (http://tools.ietf.org/html/rfc4855) for published specification, there it says that registration and the payload specification can be different documents. I am not sure that I know of such cases. In some cases there are RFC that update the registration for example by adding parameters. Regards Roni Even From: ietf-types-bounces@alvestrand.no [mailto:ietf-types-bounces@alvestrand.no] On Behalf Of Santoni Adriano Sent: Monday, March 09, 2009 9:05 AM To: ietf-types@alvestrand.no Subject: general question Hello, I have the following doubt, and would like someone to enlighten me. Is it mandatory that a media type registration be included in the RFC that defines such media type? It seems to me, if I am not mistaken, that there are several media types defined in RFCs which does not contain an explicit media type registration.. TIA, Adriano