Re: [forces] draft-ietf-forces-model-extension

[Julian Reschke <[e-mail]>]

On 2014-10-23 13:51, Jamal Hadi Salim wrote:
> On Wed, Oct 22, 2014 at 9:10 AM, Julian Reschke <[e-mail]> wrote:
>> On 2014-10-22 14:54, Haleplidis Evangelos wrote:
>>>
>>> Greetings Julian,
>>>
>>> I'm a little confused on why you think there is no backwards
>>> compatibility.
>>>
>>> LFB definitions that use the 1.0 namespace are valid in the 1.1 namespace.
>>
>>
>> Unless I'm missing something: no, they are not.
>>
>> Can you provide a 1.0 example, and show how it is valid according to the 1.1
>> schema?
>>
>
> I am trying to understand the issue.
> There is no namespace version carried in the protocol. And there is no
> changes in the protocol encoding as the result of the new namespace.
> IOW, it does not affect anything from the protocol perspective.

Now I'm very confused. The XML defined by the draft is not carried over 
the wire?

> I can see a challenge with toolkits that look at the new namespace vs old.
> Old toolkits wont be able to understand the semantics of the new namespace.

Right. So this is *not* backwards compatible. A message using the 1.1 
namespace will not be processable by a recipient that expects the 1.0 
namespace.

> New toolkits should be able to understand the semantics of both old and
> new extensions - if the author chooses to. If i understood Evangelos
> correctly: He is saying the content inside the new namespace is basically
> backward compatible. If i understood you correctly, you are saying the
> moment you say it is version 1.1 you cant talk about the content inside
> and compare it with 1.0.

You could, but it simply means that you need to write code that knows 
about both namespaces. (I understand that it's not hard to do, but it is 
very different from having nothing to do).

> All the new extensions introduced are optional. And correctly written
> s/ware will log/ignore/bailout on extensions it doesnt support.
> Are you suggesting we keep the version at 1.0?

If the rule for the 1.0 namespace is to ignore unknown elements then 
indeed it doesn't make any sense to define a new namespace.

> How does one detect there's new extensions?

By inspecting the element name and see whether it's known?

Best regards, Julian