[DDI-SRG] Proposal for DNS-based DDI URN resolution and new DDI URN Syntax

[I-Lin Kuo]

1) In both the examples
    DDI URN "urn:ddi:gesis.de:3_1:Instance.s1786.4_3"  is resolved to URL "
http://repos.gesis.org/URN?urn:ddi:gesis.de:3_1:Instance.s1786.4_3" by the
DNS record

    and the rewrite rule
    <rewriteURI uriStartString="urn:ddi:gesis.de" rewritePrefix="
http://repos.gesis.org/URN"urn:ddi:gesis.de"/>

    the agency ID "gesis.de" is somehow resolved to "repos.gesis.org". Where
is this resolution defined? This would seem to me to involve an additional
lookup into a DDI agency resolver? It's better to simply use the appropriate
domain name or subdomain name in order to avoid this extra step (as well as
the creation of a DDI agency resolver)

2) There's a conceptual confusion in what DNS is, as evidenced by the
statements:

"The DDI URN (new format)
urn:ddi:maintaining-agency-id:ddi-version-number:name-of-maintainable-object.id-of-maintainable-object.object-version-number
is related to the DNS name
object-version-number.id-of-maintainable-object.name-of-maintainable-object.ddi-version-number.maintaining-agency-id.ddi.urn.arpa."

and

"A DNS name has a maximum length of 255 characters (including all dots)"

The DNS is a system for mapping readable hostnames to IP addresses. In the
narrowest sense of DNS, it simply maps domain names to ip addresses. As an
example, with a URL such as "
http://repos.gesis.org/URN?urn:ddi:gesis.de:3_1:Instance.s1786.4_3", the
domain name of repos.gesis.org is resolved to 216.24.138.156. Then the
request is forwarded to the server at 216.24.138.156, which decides what it
wants to do with the rest of the URL. The 255 octet limit only applies to
the domain name "repos.gesis.org", not to the entire URL. There are
practical limitations on the length of the entire URL, as browsers may place
limitations on the length of the URL, but those limits are unlikely to be
reached by DDI.

So, I'd recommend that a review of the meanings of URI, URN, and URL be
done, and a lot of the references in the document to "DNS" be replaced by
URL.

3) Instead of resolving "urn:ddi:gesis.de:..." to "
http://repos.gesis.org/URN?...", I'd recommend that the resolution be to "
http://ddi.repos.gesis.org/...". While Apache can certainly rewrite any URL,
the first URL looks as if the main website server is doing the resolution,
while the second one looks as if there is a server dedicated to DDI
resolution.

On Sun, May 24, 2009 at 2:32 AM, Joachim Wackerow <
joachim.wackerow at gesis.org> wrote:

> Attached are two documents on DNS-based DDI URN resolution and on a new DDI
> URN syntax. Both documents are related.
>
> This proposal raises the question, how we can deal with this with the
> background of the new version 3.1?
>
> Achim
>
> --
> GESIS - Leibniz Institute for the Social Sciences
> Postal address: P.O. Box 122155, 68072 Mannheim, Germany
> Visiting address: B2 1, 68159 Mannheim, Germany
> Phone: +49 (0)621 1246 262
> Fax: +49 (0)621 1246 100
> E-mail: joachim.wackerow at gesis.org
> www.gesis.org/en/institute/
>
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>


-- 
I-Lin Kuo
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