FW: Should XRD allow including other XRD documents?

[Eran Hammer-Lahav <eran@hueniverse.com>]

(Please pass this to other lists you think are relevant to the conversation)


-----Original Message-----
From: Eran Hammer-Lahav 
Sent: Thursday, September 17, 2009 11:16 PM
To: 'webfinger@googlegroups.com'
Subject: Should XRD allow including other XRD documents?

The XRI TC is struggling with trying to balance between functionality and simplicity (of implementation). There is a long story behind it which you can read on the list archives (most recent threads) but it all boils down to this:

Should one XRD be able to include information from another XRD? For example, I have a blog at http://example.com and I want to use the services of xrd-depot.com to host my XRD documents because they offer APIs, security, and scale that I can't support myself. I can simply point my 'describedby' links to xrd-depot.com (ignoring trust issues for now) and let them handle everything.

But, what if I want to add something to my XRD that they do not support yet, like some new extension?

In another example, I have two blogs, each with its own XRD document which lists specific information about its APIs and services, but I want both to also include XRD links about my identity (OpenID, etc.). I want both XRDs to include the same subset of information. Should I be able to have both XRD include a third document?

The ability for one XRD to include another has many advantages, but it comes at a price. It is easy to take a single XRD document and load it into an XML parser and then iterate on the XML document tree. But if one document can include others, it means having to get and combine all the information from the multiple documents into a single set of information.

The question is, how important is the ability to do this? How problematic would it be if XRD did not allow for such includes? Also, how much more work do you think it is to support includes (it will involve some rules about striping the <XRD> root element and <Subject> from the included document)?

Please do not discuss technical solutions (yet / here), just the importance of the use cases and the implementation burden.

EHL