I would suggest using application/sdshare+atom+xml as the correct hypermedia type for sdshare. To allow for browsers and other atom clients to render sdshare feeds, I would suggest using application/atom+xml as a fallback supertype, using content-negotiation. The specification could look something like
"When content-type application/sdshare+atom+xml is requested by clients, the server SHOULD respond with application/sdshare+atom+xml. When no applicable content-type is specified or application/atom+xml is requested, the server MUST respond with application/atom+xml."
I would suggest using application/sdshare+atom+xml as the correct hypermedia type for sdshare. To allow for browsers and other atom clients to render sdshare feeds, I would suggest using application/atom+xml as a fallback supertype, using content-negotiation. The specification could look something like
"When content-type application/sdshare+atom+xml is requested by clients, the server SHOULD respond with application/sdshare+atom+xml. When no applicable content-type is specified or application/atom+xml is requested, the server MUST respond with application/atom+xml."