Database Reference
In-Depth Information
Figure 1. INSPIRE technical architecture overview
The object of our attention is the data discovery service that is in charge of both providing the dis-
covery services and the management of the metadata. Such metadata are defined to support distinct
purposes, namely:
Geodata Discovery - What geodata holds the characteristics I am interested in? This enables users to
know what geodata the organizations have and make available.
Exploration activity - Do the identified geodata contain sufficient information for my purposes? This
is documentation on the geodata that must be provided to ensure that others can use the geodata correctly.
Exploitation activity - What is the process of obtaining and using the required geodata? This helps
end users and provider organisations to effectively store, reuse, maintain and archive their data holdings.
Two kinds of metadata sets are managed by the discovery service:
the metadata data set that describes the summary information and characteristics of the available
geodata (these include human-generated textual description of geodata and machine-generated
data),
and the service metadata, that are descriptions of the service characteristics made available by the
SDI, for example services to discover geodata.
The discovery service works by comparing the users' requests for information, coming from the
Application and Geoportal Layer, with the metadata that describe available resources, following a well
know and widely developed retrieval model.
Figure 2 illustrates the three main components of a retrieval model, i.e. data representation, query
representation, and matching mechanism. In order to improve effectiveness of the discovery, repre-
sentations must be comparable and matching adequate to them (Cater and Kraft, 1989; Salton, 1989;
Bordogna, Carrara, Pasi, 1991). The matching mechanism is deputed at identifying all metadata whose
content satisfies (at least partially) users' selection conditions. In order to allow automatic matching,
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