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   Re: [xml-dev] DNS based URIs that don't imply access method

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Tim Bray scripsit:

> Hmm.... the more I learn about URNs, the fewer use-cases I can imagine. -Tim

The basic use case for URNs is having a collection of unique standardized
labels for things (computerized or not) and making them interoperate
with URLs even though retrieving representations is not practical.

Consider the news: URL scheme, which is functionally an URN.  It doesn't tell
you how to retrieve the article (unlike the nntp: scheme); relative news:
URLs make no sense; it is a unique label for something (a Usenet article)
that exists in multiple copies around the world.

Similarly, the urn:newsml: scheme provides a unique label for Real
World news articles, with four subparts: domain name of originator,
date of ownership of the domain, local-part, version number.  Again,
relative URIs make little sense here.

The ISBN and ISSN numbers for books and periodicals (the whole periodical,
not a particular number) also say nothing about retrieval and are mapped
by the urn:isbn: and urn:issn: schemes.

The urn:oid: scheme represents ASN.1 Object Identifiers, which are
hierarchical sequences of numbers used to label various computer-related
things.  For example, urn:oid: is the Internet itself.

The urn:ietf scheme labels RFCs and their friends:
ftp://ftp.isi.edu/in-notes/rfc2648.txt is an URL for that particular
instance of RFC 2648, but urn:ietf:rfc:2648 is RFC 2648 itself.

Finally, there is an URN scheme for the persons in the Internet Whois
database, people who are technical or administrative contacts for
particular DNS domains.

John Cowan
                I am a member of a civilization. --David Brin


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