[saga-rg] The URL problem

[Mark Mc Keown]

I have started looking at the SAGA strawman document and wanted
to comment on the section "The URL problem".

URL -> URI
----------

In many circumstances URI has replaced URL, see for example
Web Arch (http://www.w3.org/TR/webarch/). URIs allow you
to identify things for which there may not yet exist a 
representation - for example an output file for job
that has not started or http://host.net/tmp/file in the
SAGA document. 


Comparing URIs
--------------

Rules for comparing URIs are scheme dependent, so you cannot
compare a ftp URI to http URI, see 
http://www.textuality.com/tag/uri-comp-4 and 
http://www.faqs.org/rfcs/rfc2396.html. The SAGA document effectively
says this but I am not sure there is any need to go beyond saying
you cannot compare URIs from different schemes. 

Two URIs with different schemes can identify the same resource, 
ie they are aliases, but you cannot tell this from comparing the 
URIs. However redirection may be used to relate the URIs. For example 
a HTTP redirect: a user may get a 3XX response when attempting to
retrieve a representation of resource using HTTP which 
points him to a FTP server. So there is a question of how 
SAGA would handle a redirection - redirection of POST or PUT
in HTTP requires user input.

any scheme
----------

The W3C recommends not inventing schemes, section 2.4 of
Web Arch.
  

cheers
Mark