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RE: Scheme versioning & change management

From: Stella Dextre Clarke <sdclarke@lukehouse.demon.co.uk>
Date: Fri, 13 Aug 2004 12:33:53 +0100
To: "'Miles, AJ \(Alistair\) '" <A.J.Miles@rl.ac.uk>, <public-esw-thes@w3.org>
Message-ID: <000a01c48129$69bea300$0402000a@DELL>

These lines in an earlier message caught my eye:
"As a convention for managing URIs for concepts, I suggest that once a
concept URI has been published, preference should always be given to
deprecating and replacing with a new concept, rather than altering the
concept. 

Usually, when a concept is dropped from a scheme, another concept or
combination of concepts is added to replace it. "

Just a little health warning: concepts are not so cut and dried as you
might expect. They are slippery customers, and it is often impractical
to decide when a concept has been "changed" or when the thesaurus entry
has changed without changing the concept. Here are some of the changes
that can happen to the record for a concept:
- A new scope note is added. (Has the concept changed, or has it simply
been clarified?)
- An existing scope note is changed. (But the editor would argue, the
intended concept has not changed, only been clarified because some
people were misinterpreting it)
- New relationships are added. (No change to the original concept, only
an amendment when additional concepts were added to the thesaurus)
- New relationships are added. (The concept looks the same, its
preferred term is the same, but it never did have a scope note and in
fact the new hierarchical relationship presents it in such a way that
the concept will be perceived differently and effectively will have
changed.)
- The preferred term and one of its non-preferred terms are swapped.
(But the concept has not changed.)
- The spelling of the preferred term is changed (Just a correction, so
the concept has not changed.)
In any case, concepts tend to creep slowly and subtly over the years as
people gradually shift their patterns of terminology use.

It is often quite subjective deciding whether a thesaurus change amounts
to a change in a particular concept. The ID assigned to a particular
concept (or term) is often applied automatically without the editor even
seeing it. And that ID is often the basis for the URI. When making the
changes, the editor may do them by deleting a record completely and
starting afresh EVEN THOUGH the concept has not changed, and in the
process deriving a completely new ID and URI, or may just modify an
existing record, retaining the same ID and hence URI, but maybe this
time the concept really has changed!

Sorry to go on a bit. I am just trying to point to the danger of relying
on automatically assigned identifiers to show where concepts have or
have not changed. ( And if the IDs were added humanly, they would still
be subject to errors and subjectivity).

Also, I'm not sure I agree with the assertion that "Usually, when a
concept is dropped from a scheme, another concept or combination of
concepts is added to replace it." I suspect that what this intended to
describe was the dropping of terms rather than concepts. Concepts are
sometimes but not often dropped from schemes. Terms may be dropped, or
rather they may become non-preferred terms pointing to a different
preferred term, and during this process the original concept may be
retained or subtly modified. It is useful to track the original concept
if you can, and the network of relationships may be a more reliable
indicator than the URI.

Stella

*****************************************************
Stella Dextre Clarke
Information Consultant
Luke House, West Hendred, Wantage, Oxon, OX12 8RR, UK
Tel: 01235-833-298
Fax: 01235-863-298
SDClarke@LukeHouse.demon.co.uk
*****************************************************
Received on Friday, 13 August 2004 11:33:57 UTC

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