ELEMENT: COVERAGE
Strawman, version 1.0
fabricated by
Mary L. Larsgaard, Alexandria Digital Library/Davidson Library, UC Santa Barbara
2/24/97
Definition:
The Coverage element describes the spatial and temporal characteristics of the object or resource and is the key element for supporting spatial or temporal range searching on document-like objects that are georeferenced or time-referenced. Coverage may be modified by the qualifiers "spatial" and "temporal".
A resource may have both spatial and temporal coverages,
or just one of the two. This element may be used in describing
resources from many different fields, e.g., archaeology, art,
cartography, geography, geographic information systems, medicine,
natural sciences, etc. - any field that deals with georeferenced
information, spatial data, or time-referenced data. Thus for example,
resources describing the Grand Canyon of the United States include
text, maps, music (e.g., Ferde Grofe's Grand Canyon Suite), statistics
(e.g., number of visitors per year), works of art (such as the
panoramas that appear in the 1882 publication, "Atlas to
accompany the monograph on the Tertiary history of the Grand Canon
district"), etc.; and each could use Coverage - Spatial and
in some cases Coverage - Temporal.
Spatial information may be given by numbers (e.g.,
degrees) or by text. Temporal information may also be given by
numbers or by text.
General HTML pattern could be something like:
<META name="dc.Coverage (type=spatial, scheme=LCSH)
content="Grand Canyon (Ariz.)">
Examples of Qualifiers and Values:
There are many possible schemas; the following are some more frequently used schemas within the library world. The element value describes some sort of spatial information from the set described by the Scheme qualifier.
SPATIAL
Spatial Coverage Defined by Text
Examples of this are:
Grand Canyon (Ariz.)
2. free text:
Grand Canyon, Arizona
Spatial Coverage Defined by Numbers
A. LongLat: This qualifier specifies a latitude and
longitude. The format of a "LongLat" element is longitude
value(s) first and latitude value(s) second. The values may be:
a longitude/latitude pair (for a point); a set of four longitude/latitude
values for a bounding box (in the order westernmost longitude,
easternmost longitude, northernmost latitude, southernmost latitude);
or a set of n longitude/latitude values for any polygon or for
a line. For the planet Earth, longitude values are given in degrees
west/east of the Greenwich meridian; latitude values are given
in degrees north/south of the Equator. Earth is assumed as location;
if another planetary body is being reference (e.g., Earth's Moon),
this must be stated immediately before the coordinates are given.
Coordinates for imaginary places must have the imaginary place
noted preceding the coordinates.
Coordinates may be given several different ways:
W 120 degrees 30 minutes 10 seconds, W 118 degrees 20 minutes 3 seconds, N 80 degrees 10 minutes, N 79 degrees 50 minutes 4 seconds
OR
-120.503, -118.334, 80.167, 79.834
B. Various grids, such as the Ordnance Survey National
Grid Reference, or the UTM (Universal Transverse Mercator) grid
- I've got a 5-page handout I wrote on how the latter are derived
and expressed; if anyone really wants to know, I'll provide copy
of it.
TEMPORAL
Again, there are many possible schema. The following are a few of those frequently used in libraries.
The element value describes some sort of temporal
information from the set described by the Scheme qualifier.
Temporal Coverage Defined by Text
a. LCSH:
Cretaceous
b. free text:
Lower Cretaceous
Temporal Coverage Defined by Numbers
This should include the option to include beginning and ending date, e.g.:
… [Begin=19910101, End=19930601}
A.D. Era to December 31, 9999 A.D.: YYYYMMDD
"19970303"
and in ANSI X3.43-1986: HHMMSSSS
2. other …