Database Reference
In-Depth Information
Table 2. Specification of the temporal extent of a time series of maps
...
<gmd:extent>
<gmd:EX_Extent>
<!-- temporal Extent as unique range covering the whole melting season period -->
<gmd:temporalElement>
<gmd:EX_TemporalExtent>
<gmd:extent>
<gml:TimePeriod gml:id=”IDd2febb...”>
<gml:beginPosition>2003-04-01T11:45:30</gml:beginPosition>
<gml:endPosition>2003-08-31-T11:56:30</gml:beginPosition>
</gml:TimePeriod>
</gmd:extent>
</gmd:EX_TemporalExtent>
</gmd:temporalElement>
<!-- temporal Extent as a series of dates, each one corresponding to an image in the series -->
<gmd:temporalElement>
<gmd:EX_TemporalExtent>
<gmd:extent>
<gml:TimeInstant>
<gml:timePosition>2003-04-01</gml:timePosition>
</gml:TimeInstant>
</gmd:extent>
</gmd:EX_TemporalExtent>
</gmd:temporalElement>
<gmd:temporalElement>
<gmd:EX_TemporalExtent>
<gmd:extent>
<gml:TimeInstant>
<gml:timePosition>2003-04-15</gml:timePosition>
</gml:TimeInstant>
</gmd:extent>
</gmd:EX_TemporalExtent>
</gmd:temporalElement>
<!-- date corresponding to other images in the series -->
</gmd:EX_Extent>
</gmd:extent>
...
As regards events and observations, Dekkers, (2008) has reported that “
looking at the use of temporal
information for discovery, users may be interested in […] a particular date or time period during which
an
event
took place which is described in the
resource
”. The supporting example regards the statistics
of rainfall in a particular time period. However, though in the example there is a semantic agreement
between the event and its observations - that constitutes the content of the resource -, in many other
cases this is not applicable.
For example, if a provider has to describe the metadata of remote sensing products acquired and pro-
cessed in order to monitor a landslide that occurred in 1986, the current specification of temporal extent
just allows indicating the time of the observations (acquisitions of the satellite image) and not the time
of the event, i.e., of the landslide occurrence. Nevertheless, this can be very important information for
the user of a discovery service, because she/he can be interested in comparing the status of the landslide
in different periods of time, as they appear in distinct products. She/he must be sure that the compared
images refer to the same event, and not to distinct ones.
