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EAD  June 2003

EAD June 2003

Subject:

Re: searching on dates?

From:

"Hillyard, Matthew" <[log in to unmask]>

Reply-To:

Encoded Archival Description List <[log in to unmask]>

Date:

Thu, 19 Jun 2003 09:52:26 +0100

Content-Type:

text/plain

Parts/Attachments:

Parts/Attachments

text/plain (110 lines)

I think Bill has made things much clearer to me by pointing out the
relevance of ISO 8601 in all this. I have to confess my ignorance of it
before now, but as the ISO dates format standard, EAD is of course
completely correct to refer to it for its own handling of dates. And as Bill
points out, ISO 8601 stipulates that a date range should be captured as one
single string (using a "/" divider and not a "-") so my suggestions for a
physical 2-part division of date ranges in EAD should consequently also be
thrown-out forthwith. I was just going on the experience of having to find
work-arounds for these things in the past when actually trying to produce
working EAD applications with available indexing software.

Yes, one single string with a "/" divider *can* still be dissected
programmatically to pull out its constituent parts - we've done this here in
the past using Perl and Regular Expressions, and a nice contemporary
solution might make use XPath string-manipulation functions
(substring-before and substring-after) - but I suppose I've always thought
of normalisation as a way of avoiding having to do any further (sometimes
expensive) processing and manipulation. In other words, you do it all
beforehand?

But be that as it may - from a practical stand-point I've often found that
commercial indexing software often doesn't allowed for such additional
processing and manipulation anyway. Very often you can only feed these
search engines with the data at face value (whether it's the value of
attributes or the content of elements). You usually have to do all the
necessary processing and manipulation yourself beforehand.

The commercial indexing software we use for A2A supports specific date and
date-range indexing (and for a wide variety of common UK/US language
date-formats) but it doesn't recognise the particular ISO 8601 range format
under discussion. The software also supports most of XPath - but
unfortunately just not XPath string-manipulation functions, so
"19010904/19670327" would only ever be just that to it...

If there's a conclusion to come out of all this, then perhaps it all just
goes to reiterate the need for standards: viz. ISO 8601 and EAD (I was never
happy about having to introduce 'foreign' tags into our data, honest!). But
the same must go for for indexing / search-engine software, ie. it must
fully support all the standards - like ISO 8601 and XPath - as well. Sadly
this is not always the case, so 'work-arounds' have to be found by
developers in the field.


Matt Hillyard
A2A Developer
The National Archives
London

-----Original Message-----
From: Bill Landis [mailto:[log in to unmask]]
Sent: 18 June 2003 18:22
To: [log in to unmask]
Subject: Re: searching on dates?


I guess I don't see what the big difference is between Matt's examples:

> <unitdate normal="19010904-19670327">4 Sept. 1901 - 27 March
1967</unitdate>

[sidebar: though in the above normalization, I hope Matt meant to use the
ISO range divder "/" instead of a dash?]
and

> <unitdate firstnormal="19010904" lastnormal="19670327">4 Sept. 1901 - 27
> March 1967</unitdate>

I'm an archivist and not a programmer, so I don't know if it is easier from
a programming perspective to work with the range specified by two separate
attributes (or tags, as in Matt's other example), and a normalized date
range encoded to the specifications of the W3C DTF profile of ISO 8601. They
both represent a range of dates with first and last somehow specified. Using
2 attributes to specify the range seems a bit more verbose, and certainly
ups the encoding overhead a bit. I'd love to better understand, from a
programming perspective, why the 2-attribute (or 2-tag) option is preferable
to some.

Matt also said:

"The inability of EAD to encode a formal distinction between first and last
dates (for date range searching) has always been a stumbling-block for me
whilst trying to develop various EAD-based applications over the years. Yes,
there is the ability to encode a machine-readable, normalised version of
dates - but no actual *distinction* between first and last dates is catered
for."

EAD does allow for the formal distinction, in the same way ISO 8601 allows
for the formal distinction between the start and end of a date range. I
don't really see how labeling the distinction using 2 attributes or tags in
any way improves the designation of the start and end of a range. If it were
done consistently and predictably throughout in one way or the other, why
wouldn't that be good enough?

Bill

--
| Bill Landis
| Manuscripts Librarian, Special Collections and Archives
| The UCI Libraries, University of California
| P.O. Box 19557, Irvine, CA 92623-9557
| 949 824.3113 Voice | 949 824.2472 Fax
| [log in to unmask]


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