Creation/Modification times and Revision Numbers

Robert A. (Bob) Morris ram at CS.UMB.EDU
Tue Aug 15 21:14:01 CEST 2000

Cornelia Büchen-Osmond writes:
 > Date:         Wed, 16 Aug 2000 10:18:02 +1000
 > From: =?iso-8859-1?Q?Cornelia_B=FCchen-Osmond?= <buchen at>
 > To: TDWG-SDD at
 > Subject:      Re: Creation/Modification times and Revision Numbers
 > Just a comment:
 > I was recently told by an expert in this field that documents build on the
 > fly are usually not indexed by WWW search engines and one had to have a
 > stable document in place as well to be seen out there.
 > Cornelia
 > ----- Original Message -----

This is generally true, mostly because those engines have no
particular way to construct a query that will induce the creation of
the page.

However, /other/ software, such as that which attempts to combine the
data from several sources, may well wish to know which of those sources
is more recent, whether cached data previously obtained from a source
is stale, etc. For this reason, both a date (GMT of course) and
revision number are useful. Ideally, these would be of very fine
granularity, e.g. down to the field, but minimally they would be on
the record. If you don't do them on the field it becomes more
complicated to decide whether a datum from one database is more recent
than that from another:

Source 1 Record A: Item1(Jan 01, 2000) Item2(Feb 01, 2000)
Source 2 Record B: Item1(Feb 15, 2000) Item2(Jan 15, 2000)

Record B was modified later than Record A, but the datum in A-2 is the
more current Item2. Revision numbers are not useful across sources
unless the sources have a common revision number pool, which requires
distributed revision control.

--Bob Morris

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