Re: [Handle-info] Please help me understand the value of Handle

[Michael Judd <m.judd@griffith.edu.au>]

Hi Tim,
I'm no handle expert but here goes...
Handles are just updatable mappings
to URLs.
They allow you to publish URLs to documents
that, as long as you maintain the mapping, will always resolve.
So in your example, originally you might
have given the URL http://hdl.handle.net/98765/todo
to someone so that they could see the document at http://shield.mydomain.org/todo.txt.
(Any handle server should be able to
resolve any handle, but since handle servers themselves are suseptable
to hostname changes etc. you should use the cnri handle server (hdl.handle.net)
when giving out handle URLs as it is guaranteed not to change.)
Back to your example, after your hostname
change you would update 98765/todo
to point to http://dagger.mydomain.org/todo.txt
so that everyone who went to http://hdl.handle.net/98765/todo
would continue to see the correct document.
Originally you may have had another document at  http://whatever.mydomain.org/whatever.txt
that you created the handle http://hdl.handle.net/98765/whatever
for. This handle will still be valid as long as http://whatever.mydomain.org/whatever.txt
points to the document.
Handles with the same prefix (98765)
don't have to resolve to the same server. The prefix is just used to locate
the actual handle server.
Using DNS cnames and aliases you can
keep URLs that simply move servers or change hostnames resolving. But what
happens if an organizations domain name changes? Or what happens if the
repository software the documents exist in changes, and all the relative
links change? This is where the value of handles and other persistant URL
schemes come.
That's how I see it anyway. :)
Cheers!

Regards,

Michael Judd

Nathan Campus, Griffith University.
Brisbane 4111. Australia.

m.judd@griffith.edu.au
07 3735 3801

Tim Donnelly <tim@coalliance.org>
Sent by: handle-info-admin@cnri.reston.va.us

23/03/2007 07:39 AM

Please respond to
tim@coalliance.org

To	handle-info@cnri.reston.va.us
cc
Subject	[Handle-info] Please help me understand the value of Handle

I am confused on the way Handles work.  Let me explain
by way of an example.

I have a prefix, for the sake of argument 98765.  I have created a handle 98765/todo that points to the URL http://shield.mydomain.org/todo.txt.  If I look at the handle in the Admin tool it shows a data value of the URL.

But, what happens if at some point in the future, the name of the host changes from shield.coalliance.org to dagger.mydomain.org?  That handle is now broken, correct?

I thought the whole point of Handles was to create a way to be able to find information regardless of changes such as I described.

The way I envisioned the Handle service working is more like this:

98765 would actually resolve to http://shield.mydomain.org, therefore handles I create would only include the final destination at that location (todo.txt in my example above). So, the Handle 98765/todo would equal http://shield.mydomain.org/todo.txt. Then, if I later changed shield to dagger, I would have to update my siteinfo with the Global Registry, telling it that all 98765 prefixes now belong to dagger.mydomain.org.

The way it appears to actually work to me is:  

The 98765 prefix is simply used by the Global Registry to tell the proxy server which local handle server it should look to to resolve.  So, the proxy server looks up 98765 and knows to send the request to my local server at IP 192.168.0.1.  The local server then says "todo" is equal to the URL and redirects the users browser to that URL hard coded into the handle.

I have tested this by creating a Handle with the URL of todo.txt, no domain info included.  When I attempt to resolve it I get an error that it cannot be found.

I'm sure this isn't making much sense but I am having a hard time wrapping my brain around these concepts.

Thanks in advance.

Tim Donnelly
Systems/Network Administrator
Colorado Alliance of Research Libraries
(303)759-3399 x106

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