Mike Taylor wrote:
> Going back to someone's point about living in the real
> world (sorry, I forget who), the Inconvenient Truth is that 90% of
> programs and 99% of users, on seeing an http: URL, will try to treat
> it as a link.  They don't know any better.

And they can't know any better because there is no discernible 
difference to either a human being or a program. There is nothing about 
an http URI that tells you what it is being used as and whether there is 
anything at the other end until you send it out over the net where it 
will be processed by http.[*] So we have two things that are identical 
in form but very different in what we can do with them. Isn't this a bad 
idea? There are probably solutions to this; perhaps a particular port 
that indicates that the identifier cannot be dereferenced (I'll suggest 
666) or one that gets data about the resource identified (11111 would 
do). But it seems to me that the best solution is to use a URI scheme 
that isn't the same as a URI scheme that is already used for a protocol.

And before someone comes up with the statement that when you have a URL 
you don't know beforehand if you will get something or will get a 404 
error, and therefore it's the same as a URI, let me remind you that 404 
is indeed an *error code* that means 'Not found', which implies that 
*not finding anything* is an error. It can't, however, tell you if there 
*should* have been something there, or if there never was supposed to be 
something there, but it does mean that an error has occurred.And if you 
want to make the argument that one could return some other http return 
code, that implies having some program responding to the URI in response 
to http, which is a form of derefencing. If you're going to do that, you 
might as well include some real info about the thing identified.


[*] This is one of the things that I've always disliked about the DOI -- 
it is an identifier for the resource, but it doesn't necessarily resolve 
to the resource. In fact, some DOIs resolve to the resource, some 
resolve to a page with metadata for the resource, some go to a 
publisher's home page and the resource isn't available in digital 
format. I understand why this is the case, but it makes it hard for 
humans and machines because isn't clear what you will get when you 
dereference a DOI (and you are encouraged to dereference them because 
they are a sales mechanism). I think that not getting what you want and 
expect when clicking on a link is one of the things that discourages 
users (machines just trundle happily along, but many of us are not 

Karen Coyle / Digital Library Consultant
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