Re: [regext] OK, What Next? (was RDAP Extensions Approach Analysis v2)

["Hollenbeck, Scott" <[e-mail]>]

> -----Original Message-----
> From: Mario Loffredo <[e-mail]>
> Sent: Monday, July 18, 2022 4:40 AM
> To: Gould, James <jgould=[e-mail]>; [e-mail]
> Cc: Hollenbeck, Scott <[e-mail]>; [e-mail]
> Subject: [EXTERNAL] Re: [regext] OK, What Next? (was RDAP Extensions
> Approach Analysis v2)
>
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> I agree with James.
>
> The drawback of Approach A is that even an additive change to an existing
> extension would result in a breaking change to the RDAP service. As a
> consequence,  servers should always manage the transition from two
> subsequent versions of an extension.

Please explain how there's a breaking change. Let's assume that we have an 
extension named "foo version 1" identified by the prefix "foov1". "foov1" is 
registered with IANA, returned in the server's rdapConformance data structure, 
and used to prefix extension elements.

Now assume that a second version of the extension (foo version 2) exists, 
identified by the prefix "foov2". "foov2" is also registered with IANA, 
returned in the server's rdapConformance data structure, and used to prefix 
extension elements.

If the server supports only "foov1" or "foov2", it returns only one of those 
values in the rdapConformance data structure, accepts only extension elements 
prefixed with the supported value, and returns only extension elements 
prefixed with the supported value. If a server supports both "foov1" and 
"foov2", it returns both values in the rdapConformance data structure, accepts 
extension elements prefixed with either value, and returns extension elements 
prefixed with the value that matches the requested value. So how does this 
transition scenario not work?

Server supports "foov1" and returns that value in the rdapConformance data 
structure. The server accepts requests and returns responses prefixed with 
"foov1". The client sends requests and receives responses prefixed with 
"foov1".

At some point in the future a new version of "foo", identified by "foov2", 
exists. The server enters a transition period and announces support for both 
extensions by returning both values in the rdapConformance data structure. It 
accepts extension elements prefixed with either value and returns extension 
elements prefixed with the value that matches the requested value. The client 
sends requests and receives responses prefixed with either "foov1" or "foov2" 
depending on which value of the extension they support.

Time passes, and the transition period ends. The server deprecates support for 
"foov1" and announces support for only "foov2" by returning only that value in 
the rdapConformance data structure. The server accepts requests and returns 
responses prefixed with "foov2". The client sends requests and receives 
responses prefixed with "foov2".

Where's the breakage here? In both cases, the client and server can identify 
extension elements by doing a simple pattern match for "foov1" or "foov2".

Scott