XRI as structured URI

Inspired by a recent 
blog entry by Mark Nottingham ( http://www.mnot.net/blog/archives/000137.html ), 
and some internal requirements about describing "XRI namespaces", I decided to 
sit down and think about how one could structure the parsing and (more 
importantly) construction of XRIs from a template and a set of data fields. 

 

For example, lets 
say I have an XRI template for XRIs identifying houses on a trash collection 
route

 

xri:@TrashCompany/<city>/<street>/<number>

 

Examples of this XRI 
would include:

 

xri:@TrashCompany/belmont/ralston/1000

xrI:@TrashCompany/oakland/telegraph/400

 

I want to be able to 
describe this template more formally, however, and so I set about seeing what I 
could do leveraging XML tools. 

 

The first step was 
to define a simple XML schema for representing the structure of a XRI. This 
representation should be fairly rivial to convert to and from the form that we 
are defining in the XRI spec:

 

<xri>

  
<content>

    
<segment><pnode>@</pnode><pnode>TrashCompany</pnode></segment>

    
<segment><pnode 
id="city">...</pnode></segment>

    
<segment><pnode 
id="street">...</pnode></segment>

    
<segment><pnode 
id="number">...</pnode></segment>

  
</content>

 

The next step was to 
add some information about what are fields:

 

  
<fields>

    
<description ref="city">

      
<type>http://www.w3.org/2001/XMLSchema#string</type>

      <summary>The city 
where this location is</summary>

    
</description>

    
...

  
</fields>

</xri>

 

These above xml 
document constitutes a "template". To fill in the template (something an 
application constructing an XRI might do), a simple XML file of the following 
form is used:

 

<data>

  
<variable>

    
<name>city</name>

    
<value>belmont</name>

  
</variable>

</data>

 

Next, I defined an 
XSL stylesheet that takes the template above and "plugs in" the data fields. The 
result is an XML file contains the 
<xri><content>...</content></xri> with all the data 
fields filled in - in other words a structured XRI with data fields filled in. 
This can easily be transformed back into the form of the XRI in the 
specification:

 

<xri>

  
<content>

    
<segment><pnode>@</pnode><pnode>TrashCompany</pnode></segment>

    
<segment><pnode>belmont</pnode></segment>

    
<segment><pnode>ralston</pnode></segment>

    
<segment><pnode>1000</pnode></segment>

  
</content>

</xri>

 

I think the approach 
of converting the XRI to XML and processing it there with XML tools is 
interesting. This is just a first stab at this approach. 

 

I'm NOT suggesting 
that this stuff become formalized by the TC, I'm merely suggesting that there 
are a lot of uses XRIs can be put to, and we can start playing with them NOW. 

 

The XSL and sample 
XML files are attached in a zip file. 

 

    
-Gabe

xrixml.zip