Web Resource Identity

David Megginson david at megginson.com
Fri May 28 20:24:40 BST 1999

Paul Prescod writes:
 > David Megginson wrote:
 > > 
 > > But you cannot always take two references and determine if they do
 > > *not* refer to the same object -- that depends on the design.
 > "Do these refer to the same object?" => Yes/No/Maybe
 > I'm not familiar with a system like that. Can you give an example?

You will often end up with two objects that represent conceptually the
same thing but cannot be proven equivalent (two medicare records, for
example); in fact, you may even have objects that share the same set
of attributes but cannot be proven equivalent.  There's also the case
of lazy Java programmers who don't override java.lang.Object.equals()
(that represents a significant percentage of existing Java code, I'd

 > Obviously boolean logic is MUCH easier to work with than tri-nary
 > logic.

No, in the case of URLs, it's still binary:

  "Are these known to refer to the same object?" => Yes/No

And while a cononical URL is an easy extension to HTTP, the
infrastructure to support it is another issue -- do I have to
guarantee, for example, that a gzipped tar file of the same version of
the Linux kernel source at two different mirrors return the same
canonical URL?

All the best,


David Megginson                 david at megginson.com

xml-dev: A list for W3C XML Developers. To post, mailto:xml-dev at ic.ac.uk
Archived as: http://www.lists.ic.ac.uk/hypermail/xml-dev/ and on CD-ROM/ISBN 981-02-3594-1
To (un)subscribe, mailto:majordomo at ic.ac.uk the following message;
(un)subscribe xml-dev
To subscribe to the digests, mailto:majordomo at ic.ac.uk the following message;
subscribe xml-dev-digest
List coordinator, Henry Rzepa (mailto:rzepa at ic.ac.uk)

More information about the Xml-dev mailing list