XRI's in xml namespaces

[Dag Arneson]

I'm not an expert, but I'm reading RFC 3986 section 3.2, and my 
impression is that XRI syntax violates the authority syntax described 
there, particularly the use of the @ symbol (which is specified to 
separate the user information from the host) and also the clause "URI 
producers should use names that conform to the DNS syntax" for the host.

So, by my reading, in the strictest of senses "xri://=foo" and 
especially "xri://@foo" are not URIs according to RFC 3986.

I don't think that this is likely to be an issue practically, but it 
seems worth consideration.

Also worth noting is that if one of the slashes is dropped, they become 
valid URIs with no authority, and the XRI authority becomes part of the 
URI path, which has few restrictions placed on it by 3986.


Drummond Reed wrote:
> Grant, sorry, I'm a day behind on this thread, but I wanted to reinforce
> Thomas's answer:
> 
> Yes, it is legal to use an XRI as a XML namespace attribute (or anywhere
> element or attribute in XML that uses an "anyURI" datatype). Because the
> anyURI datatype accepts either an IRI or a URI, the only requirement is that
> you make sure the XRI is in either IRI-normal form or URI-normal form.
> 
> Once transformed (as defined in the XRI spec), an XRI is just an IRI or URI
> so no XML or IRI/URI parsers should have any problem with it.
> 
> Also note that many XRIs are identical in XRI-normal form, IRI-normal form,
> an URI-normal form, i.e., no transformation rules apply. 
> 
> An example of all of this is the XRIs used for the XML namespace attributes
> in XRDS documents, e.g.:
> 
> <?xml version="1.0" encoding="UTF-8"?>
> <XRDS ref="xri://=foo">
>     <XRD xmlns="xri://$xrd*($v*2.0)">
>         <Query>*foo</Query>
> ...
> 
> 
> =Drummond 
> 
> -----Original Message-----
> From: yadis-bounces at lists.danga.com [mailto:yadis-bounces at lists.danga.com]
> On Behalf Of Grant Monroe
> Sent: Monday, June 12, 2006 2:58 PM
> To: Thomas Broyer
> Cc: yadis at lists.danga.com
> Subject: Re: XRI's in xml namespaces
> 
> On 6/12/06, Thomas Broyer <t.broyer at gmail.com> wrote:
> 
>>2006/6/12, Grant Monroe:
>>
>>>Is it technically valid to use an XRI in an XML namespace attribute?
>>>I was looking at the W3C recommendation on XML namespaces,
>>>http://www.w3.org/TR/xml-names11/, and it looks like the value of an
>>>XML namespace attribute must be an IRI. While there may be rules to
>>>convert XRIs to IRIs, current parsers might barf.
>>
>>>From what I read about XRIs, if you apply escaping rules from section
>>2.3.2 (from XRI Syntax 2.0), you should have an IRI, usable as a
>>namespace.
>>Could someone more used to XRIs confirm this?
>>
>>
>>>I bring this up because .Net xml parsing converts xml namespaces to
>>>Uri objects.
>>
>>Are you sure?
>>I can't find a reference to Uri in Microsoft's docs:
>>XmlNode.NamespaceURI is a string:
>>
> 
> http://msdn.microsoft.com/library/FRE/cpref/html/frlrfsystemxmlxmlnodeclassn
> amespaceuritopic.asp
> 
>>XmlQualifiedName.Namespace is a string:
>>
> 
> http://msdn.microsoft.com/library/FRE/cpref/html/frlrfsystemxmlxmlqualifiedn
> ameclassnamespacetopic.asp
> 
>>XmlReader.NamespaceURI is a string:
>>
> 
> http://msdn.microsoft.com/library/FRE/cpref/html/frlrfsystemxmlxmlreaderclas
> snamespaceuritopic.asp
> 
>>and finally, XmlNamedNodeMap (which is also the base class for
>>XmlAttributeList) and XmlNamespaceManager use strings:
>>
> 
> http://msdn.microsoft.com/library/FRE/cpref/html/frlrfsystemxmlxmlnamednodem
> apclasstopic.asp
> 
> http://msdn.microsoft.com/library/FRE/cpref/html/frlrfsystemxmlxmlnamespacem
> anagerclasstopic.asp
> 
>>and having used ILDAsm on Microsoft's XmlTextReader and XmlScanner, I
>>can't find any URI parsing...
>>
>>--
>>Thomas Broyer
>>
> 
> 
> Well, it looks like I was smoking a bit of crack about the xml parser
> turning namespaces into Uri objects. .Net xml parsing works just fine.
> I had an unrelated bug that lead me to this issue. I am still a bit
> troubled by using broken XML even if it isn't an implementation
> hurdle, though.
> 
> --
> Grant Monroe
> 
> 
>