Database Reference
In-Depth Information
Table 1. Temporal metadata elements in INSPIRE Implementing Rules
Metadata element Metadata sub-element
Definition
Temporal reference -
It addresses the Directive's requirement to have information on the temporal dimension
of the data (Article 8-2 (d)). At least one of the following metadata sub-elements shall
be provided
Temporal reference Temporal extent
It defines the time period covered by the content of the resource. This time period can
be expressed as:
• an individual date,
• an interval of dates expressed through the starting date and end date of the interval; or
• a mix of individual dates and intervals of dates.
The default reference system shall be the Gregorian calendar, with dates expressed in
accordance with ISO 8601
Temporal reference Date of publication
This is the date of publication of the resource when available, or the date of entry into
force
Temporal reference Date of last revision
This is the date of last revision of the resource, if the resource has been revised
Temporal reference Date of creation
This is the date of creation of the resource, if it has not been revised
of time values to be adopted either in expressing dates or time periods and to suggest how to preserve
precision in exchange or conversion processes.
However, these recommendations are still limited, with respect to both the requirements of time
stamping by metadata providers, and the representation of the temporal search conditions necessary to
geodata users.
EXTENDING TEMPORAL METADATA AND MANAGING TIME SERIES
Based on actual experience gained in the European Projects IDE-Univers (http://www.ideunivers.eu)
and AWARE (http://www.aware-eu.info), we verified the usefulness of series of temporal datasets and
realized that some extensions should be adopted to improve temporal characterization of datasets and
dataset series in the metadata of an SDI. In fact, as discussed in the previous paragraph, the current
specification of INSPIRE (European Commission, 2009) does not allow specifying the time relative to
the occurrence of the event that is observed in one, several or a series of spatial data, nor their temporal
granularity. As experienced in our practice, these aspects could not be considered irrelevant for INSPIRE
applications as argued also in (Dekkers, 2008). Therefore, in the following subparagraphs we first in-
troduce a proposal for managing temporal series of data sets, and then discuss the need for metadata
extensions in the temporal domain.
Temporal Data Set Series
In many real applications it is worth pointing out that a set of geographic resources is a collection of
data that share common spatial properties (e.g., they cover the same area, they are the products of the
same application) but are distinct with respect to their temporal attribute. An example could be the set
of snow cover maps of the Alpine region, resulting from the processing of satellite images taken in dif-
ferent days along one melting season.
