Backwards compatibility

[David Fuelling]

Josh,

Just a point of clarification -- As worded, your #1 says that any OpenId 2.0
message would work in any OpenId 1.1 system, which (from my perspective)
implies that the 2.0 protocol cannot implement any (significant) message
features that aren't defined in 1.1....which would tend to imply that the
two protocols are identical (since 1.1 is already defined).

Are you really meaning to ask the following instead:

#1R: OpenId 2.0 systems MUST implement and support all of the messages in
OpenId 1.1.

#2R: It is possible for implementations to differentiate between OpenID
1.1 and 2.0 and to construct appropriate messages. In essence, it's a
different protocol, and #1R is not required.



Thanks!

David Fuelling

> -----Original Message-----
> From: specs-bounces at openid.net [mailto:specs-bounces at openid.net] On Behalf
> Of Josh Hoyt
> Sent: Wednesday, September 20, 2006 4:31 PM
> To: specs at openid.net
> Subject: Backwards compatibility
> 
> When making and evaluating proposals, there have been many references
> to backwards compatibility. I'm not sure that everyone has the same
> idea what it means to be backwards compatible.
> 
> There are at least two meanings that I can see:
> 
> 1. Messages that are valid OpenID 2.0 messages are also valid OpenID
> 1.1 messages
> 
> 2. It is possible for implementations to differentiate between OpenID
> 1.1 and 2.0 and to construct appropriate messages. In essence, it's a
> different protocol.
> 
> I've been focused on maintaining (1). How do you see it?
> 
> Josh
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