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gils: Re: Time Period Elements in the GILS Profile.

gils: Re: Time Period Elements in the GILS Profile.

Re: Time Period Elements in the GILS Profile.

Eliot Christian (echristi@usgs.gov)
Tue, 10 Sep 1996 13:44:25 -0400 

Message-Id: <2.2.32.19960910174425.0071a924@isdmnl.wr.usgs.gov>
Date: Tue, 10 Sep 1996 13:44:25 -0400
To: gils@cni.org
From: Eliot Christian <echristi@usgs.gov>
Subject: Re: Time Period Elements in the GILS Profile.


Doug Nebert wrote on 9/4/96:
> 
> [...]
> This set of elements also creates a problem for us in that it is in
> conflict with the Geospatial "GEO" profile being developed that is
> supposed to inherit many bib-1 and GILS elements.  To achieve meaningful
> search across both types of servers (it is desired that GEO servers be
> approachable as GILS servers) the semantics of the time content elements
> should be the same. In GILS, the time reference appears to use a USMARC
> convention that is not explained in the Profile. In GEO, time can be
> represented as a single date-time, multiple discrete date-times, or a
> range of date-times (beginning and ending times of coverage).  These
> constructs are important in providing users with a sense of temporal
> coverage that can be visualized relative to other data entries, and to
> help in search for time-critical data.
> 
> Are the structured time fields being used as searchable elements by
> default?  If not, they should be. If so, we need to assure that there is
> a full and unambiguous mapping between the semantics of the GILS and GEO
> elements for time if they are to be interoperable.

In GILS, we have two structured elements that are used to describe time
periods: Time Period Structured (Use Attribute 2044) and Available Time
Structured (Use Attribute 2019). Both of these are defined to be 
represented using "USMARC structure", i.e., the format associated with 
USMARC tag 045, subfield "c". 

As I understand from Rebecca Guenther, the USMARC format allows for
repeating the subfield dates and setting an indicator to signify that 
the dates are to be treated as a time period. There is no such indicator 
in GILS, and the structured time period elements are not repeatable. So, 
it is clearly inadequate to simply reference USMARC for the defintion of 
the GILS structured time period elements.

The proposed GEO Profile defines a structure Time Period of Content (Use
Attribute 3013) as follows:

 Time Period of Content (compound)
       Time Period Information
         Single Date/Time
           Calendar Date (valued)
           Time of Day (valued)
         Multiple Dates/Times
           Calendar Date (valued)
           Time of Day (valued)
         Range of Dates/Times
           Beginning Date (valued)
           Beginning Time (valued)
           Ending Date (valued)
           Ending Time (valued)

Does anyone object to using the GEO Profile structure definitions for the
GILS elements Time Period Structured and Available Time Structured?

Eliot Christian, US Geological Survey, 802 National Center, Reston VA 20192
echristi@usgs.gov  Office 703-648-7245  FAX 703-648-7069  Home 703-476-6134

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