To:
James Gould <jgould@verisign.com>
cc:
EPP Provreg <ietf-provreg@cafax.se>
From:
Bernie Hoeneisen <bernie@ietf.hoeneisen.ch>
Date:
Mon, 25 Jan 2010 22:05:30 +0100 (CET)
In-Reply-To:
<C78363CA.3701F%jgould@verisign.com>
Sender:
owner-ietf-provreg@cafax.se
User-Agent:
Alpine 2.00 (DEB 1167 2008-08-23)
Subject:
Re: [ietf-provreg] XML Schema versioning in 4310bis
Hi James On Mon, 25 Jan 2010, James Gould wrote: > I had multiple private messages associated with this, but on the list > the only message that directly references is from me on December 8th: > > http://www.cafax.se/ietf-provreg/maillist/2009-12/msg00000.html Thanks for the pointer. Sorry, but in this case you can not declare it "consensus", as there was not even a sufficient public disussion to reach a consensus. > The other indirect item is the goal of “XML schema is backward > compatible”, which is included in multiple messages on the list. Well, I'd say many people are just not aware of this work going on. e.g. I only spotted it accidently today, which leads to the other discussion about making EPP work in the IETF official... > Changing the URI (version number) would break this goal, since clients > would be required to upgrade their clients to use the new URI, assuming > that a server only supports the new draft. The servers could support > two URI’s, which is technically feasible but not simple. I don't think the burden should be on the clients. Servers will have to implement both versions during a transition period, and Clients will gradually upgrade to the new version. > > What are the disadvantages if the XML schema version number was changed to > > urn:ietf:params:xml:ns:secDNS-1.1 ? > > 1. Clients that support 1.0 would be required to upgrade to 1.1 for servers that support 1.1. Backward > compatibility does not provide a huge benefit if the URI changes. Client EPP SDK’s need to be > upgraded to support this, where if backward compatibility is maintained the clients don’t need to do > anything. If servers are implementing both versions, clients do not need to implement both versions during a transition period. If you keep the schema backward compatible (as you intend to), there is little complexity added to the server. > 2. Servers might have to support more then one version at a time to migrate users to the new draft. I > don’t know of any servers supporting multiple versions of anything now, so adding this requirement > for a backward compatible scheme seems kind of overkill. Well, I implemented such a scenario with two XML schema versions on a productive EPP server with extension RFC 5076, which had a change in the XML schema during the standardization process. It worked just fine. > I don’t see a huge advantage of changing the URI, other then clarity in > the EPP greeting. Clients can start exercising the new features of the > new draft when the servers supports it as an option instead of as a > requirement. I don't think that it is a good idea to make a standard that expects such a behavior. Servers and clients might run into (unexpected) error cases, which are difficult to catch due to ambiguity in the standards, which is to be avoided Another thought: Have you considered to make a complete new XML Schema for the new functionality, leaving the existing XML Schema untouched? [Note: I have not studied in detail whether or not such an approach is at all feasible.] cheers, Bernie