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Re: Best Practice for URI construction?

• To: "Costello, Roger L." <costello@m...>
• Subject: Re: Best Practice for URI construction?
• From: Philippe Poulard <Philippe.Poulard@s...>
• Date: Fri, 09 Dec 2005 16:30:31 +0100
• Cc: XML Developers List <xml-dev@l...>
• In-reply-to: <B8415163A689094689542C617ECA036650F585@I...>
• References: <B8415163A689094689542C617ECA036650F585@I...>
• User-agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.7.7) Gecko/20050511

Costello, Roger L. wrote:
> Hi Folks,

hi, Roger

>  
> A URI is used to "identify" a resource:
>  
> /A Uniform Resource Identifier (URI) is a compact sequence of characters 
> that _identifies_ an abstract or physical resource./[1]
>  
> I would like to bound the following discussion by considering just URLs 
> that use the http scheme.
>  
> As I see it, there are two main approaches to constructing a URL to 
> identify a resource:
>  
> *Approach 1. URL Construction using Parent/Child Relationships*
>  
> Here's an example of a URL that uses this approach:
>  
> http://www.location.org/US/MA/Boston
>  
> After the [host] (www.location.org <http://www.location.org>) there are 
> a series of slash-delimited names.  The name to the left of a slash is 
> the parent.  The name to the right of a slash is the child.
>  
> *Approach 2. URL Construction using Key-Value Pairs plus Conjunction*
>  
> This second approach is exemplified with this URL:
>  
> http://www.location.org?country=US&state=MA&city=Boston 
> <http://www.location.org?country=US&state=MA&city=Boston>
>  
> After the [host] there is the query string delimiter (?) followed by one 
> or more key=value pairs ANDed together.
>  
> Hybrids of the above two approaches are also possible.  For example:
>  
> http://www.location.org/US/MA?city=Boston
>  
> *Questions*
>  
> (1) The above URLs (I believe) are expressing the same thing - they are 

it's a convention at http://www.location.org/ : RFCs doesn't say that 
they are the same

> identifying the same resource.  So which is "better"?

http://www.location.org?country=US&state=MA&city=Boston
http://www.location.org?state=MA&city=Boston&country=US
are the same

http://www.location.org/US/MA/Boston
http://www.location.org/MA/Boston/US
are not

however, it seems that at http://www.location.org/ they decide they are 
the same : it's a convention

>  
> (2) As was noted at the top, the purpose of a URL is to "identify" a 
> resource.  Can every resource in the universe be identified using the 
> above two approaches?  Are there resources that do not lend themselves 
> to identification using the above two approaches?
>  
> /Roger
>  
> [1] http://www.gbiv.com/protocols/uri/rfc/rfc3986.html
>  
>  

IMHO,

"identify" is not the term that I would use for URLs ; we can say more 
precisely that :
URL "localizes" a resource
and URN "names" a resource

what you intend to do is something closer to name than localize when you 
use the key-value pairs ; so, URN would be more suitable :
urn:my-scheme:US:MA:Boston
               |  |  |
               |  |  this field is defined as the city
               |  this field is defined as the state
               this field is defined as the country

but it is not usable as-is : it may be used internally, but the 
publishing form of this URN could be :

http://www.location.org?country=US&state=MA&city=Boston
or
http://www.location.org/US/MA/Boston
or
http://www.location.org/US:MA:Boston

ha ! this becomes very useless :)

not really : the benefit of such a neutral approach is the ability to 
publish your data to multiple targets, that's why I prefer it ; it's 
easy with XML to have neutral URIs in source documents and to map them 
when publishing

from the client point of view, how to process the URLs ?

in your case, it is obvious that the "fields" can be change with other 
values ; this can be done easily thanks to HTML forms, because the HTTP 
GET method can produce this kind of URI :
http://www.location.org?country=US&state=MA&city=Boston
but in the other case, it is not obvious from a form to produce it :
http://www.location.org/US/MA/Boston
which requires smart URL manipulation with javascript

so, make your choice ; why don't you use both ?

-- 
Cordialement,

            ///
           (. .)
  -----ooO--(_)--Ooo-----
|   Philippe Poulard    |
  -----------------------

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