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Bob Wyman scripsit:
> Dave Winer's suggestion that GUID be used to disambiguate
> versions of items does, in fact, require that a unique GUID be
> assigned to every new version or variant of an item. This is, of
> course, one of the big reasons why his proposal has not been widely
> implemented.
IMHO the urn:newsml: scheme is a huge win in this respect. The details
are at http://www.ietf.org/rfc/rfc3085.txt , but the general scheme is
this:
urn:newsml:example.com:20040203:SLUG:1
Of these six parts, "urn" and "newsml" are fixed. The third part is a domain
which the issuer of the item owns. The fourth part gives an ISO 8601 date,
such that the issuer owned the domain during the whole of that date. This
allows for the fact that more than one entity can control a domain name
at different times.
The fifth part is a string that taken jointly with the third and fourth parts makes a string to the issuer. The sixth part is a version
number, which must be positive (zero is forbidden) and which must increase
with every new version (it need not increase by 1), possibly followed by "A" or
"U", which mean that this item is metadata-only or a diff respectively; otherwise,
it is a replacement.
With this scheme, there is a globally unique URI for every version of every
item, but it is trivial to find the latest (or earliest, or whatever) version
of a particular item identified by the first five parts.
Reuters Health URNs look like this:
urn:newsml:reutershealth.com:20040203:elin001:1
The domain-valid date doubles as the date of first publication, and the
slug specifies the newswire and an arbitrary three-digit number within that
newswire: taken jointly with "reutershealth.com", this represents a unique
story. This particular one is the first and only version.
--
Using RELAX NG compact syntax to John Cowan
develop schemas is one of the simple http://www.reutershealth.com
pleasures in life.... http://www.ccil.org/~cowan
--Jeni Tennison <jcowan@reutershealth.com>
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