"However, profile exchange is optional"

[Martin Atkins]

sites at thirdvisit.co.uk wrote:
> 
> And if so, why should this NOT go in the v1.0 spec for Yadis?
> 

YADIS doesn't (or rather, shouldn't) specify any services of its own,
since it's simply a mechanism for describing the available services.
Profile exchange is just another service. For example, LID 2.0 Profile
Exchange is one example of a profile exchange mechanism that can be
declared through YADIS. Others may arise later.

Anyone can invent new services built on top of YADIS without the need
for approval from the YADIS spec. That's the whole point of YADIS.