[OpenID] Summarizing my grouse with XRD

[Santosh Rajan]

So it is now clear to me that identity protocols cannot use the XRD
specification "as is". There has to be a new "Identity Resource Descriptor"
specification sitting in between XRD and all identity protocols that draw
from XRD.
I will explain the problem with an hypothetical example. Lets say webfinger
were to specify that the <Subject> of the XRD is not required. And a future
OpenID spec mandates the use of <Subject>, because the OpenID folks felt
that XRD with no Subject was a security risk. The future OpenID Spec will
not be able to use the webfinger protocol (which according to current
thinking it may want to).

In any case an "Identity Resource Descriptor", without a Subject to describe
it, is entirely meaningless to me. So a new identity Layer for XRD is called
for that mandates the use of <Subject> in all Identity Resource Descriptors.
(IRD's).

On Thu, Oct 22, 2009 at 8:46 AM, John Bradley <ve7jtb at ve7jtb.com> wrote:

> I suppose if we were starting fresh we could have called it RDML.
>
> I don't know that there is a meaningful distinction between a document
> format like  OpenDocument and meta-markup language like SAML.   Technically
> they are the same.
>
> The XRI-TC will also be producing a XRI 3.0 spec that will use this updated
> XRD document specification.
>
> Webfinger and others may also produce processing specifications for XRD or
> profiles of XRD.
>
> XRD is NOT an identifier.
>
> XRDS as currently used in openID discovery stands for eXtesable Resource
> Descriptor  Sequence.
>
> Yadis never made any use of the Sequence feature so we made it optional.
>
> Hense the main document format spec is now called XRD and not XRDS.
>
> I know people are planning on using it with a multitude of different
> identifiers including email addresses.
>
> It is still XML and the document is a meta-data descriptor not an
> identifier.
>
> John B.
>
> On 2009-10-21, at 11:13 PM, Santosh Rajan wrote:
>
> In other words now you are saying that XRD is another markup language like
> HTML and SAML. In which case you should be calling it "XRML" for Extensible
> Resource Markup Language.
> So what started as a "Descriptor" has morphed into a "Markup Language".
>
> So this gives scope for someone else to write the "REAL" Extensible
> Resource Descriptor Specification on top of XRML.
>
>
> On Thu, Oct 22, 2009 at 2:24 AM, John Bradley <ve7jtb at ve7jtb.com> wrote:
>
>> XRD is a XML document spec.
>>
>> On 2009-10-21, at 5:21 PM, John Kemp wrote:
>>
>>  John Bradley wrote:
>>>
>>>> It means that some protocol that is using XRD is defining the subject
>>>> via some external mechanism.
>>>>
>>>
>>> So the XRD spec. is a template spec. meant to be simply incorporated by
>>> reference into other specs. I guess?
>>>
>>>  Like other XML specs eg SAML 2.0 it can be used multiple specifications
>> that process XML documents.
>>
>> External specs can profile the XRD spec.
>>
>>  In the HTTP protocol case there may be an implicit subject based on the
>>>> identifier that is being resolved.
>>>>
>>>
>>> As mentioned earlier, if the _subject_ of the XRD is identified
>>> (implicitly) by the same URI used to retrieve the XRD itself, then that
>>> seems rather circular.
>>>
>>>  The XML document describes a resource and provides links to associated
>> resources.
>> A HTML page doesn't need to explicitly say what URI it is retrieved from
>> in its internal markup.
>>
>> Like with HTML sometimes the subject is defined by the transport or other
>> external method.
>>
>> Thanks
>> John B.
>>
>>  All normal http caching would apply in the http: case.
>>>>
>>>
>>> Sure, I'm not quibbling with caching...
>>>
>>>  In the IMI/SAML case we have discussed pushing a XRD as a
>>>> assertion/claim.
>>>> In that case the subject may be the same as the saml:NameID in the
>>>> containing saml:Assertion.
>>>> It could perhaps be argued that putting a xrd:Subject and signature
>>>> inside a signed saml:Asertion is un-neccicary.
>>>> Suffice to say it is up to the protocol using XRD to decide what to make
>>>> of a XRD without a xrd:Subject.
>>>>
>>>
>>> OK, I think I've understood ;)
>>>
>>> Cheers,
>>>
>>> - johnk
>>>
>>>  John B.
>>>> On 2009-10-21, at 3:09 PM, John Kemp wrote:
>>>>
>>>>> John Bradley wrote:
>>>>>
>>>>>> Yes a XRD can be used for identity.  In that case it should be a
>>>>>> signed XRD (with Subject)
>>>>>> However a XRD can be used to describe any resource (URI).
>>>>>>
>>>>>
>>>>> What does it mean then (in XRD terms) if an XRD doesn't identify the
>>>>> resource it describes (ie. it doesn't have a subject)?
>>>>>
>>>>> - johnk
>>>>>
>>>>
>>>
>>
>
>
> --
> http://hi.im/santosh
>
>
>
>


-- 
http://hi.im/santosh
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