Global Drought Monitoring Service through the GEOSS Architecture ...
Global Drought Monitoring Service through the GEOSS Architecture ...
Global Drought Monitoring Service through the GEOSS Architecture ...
You also want an ePaper? Increase the reach of your titles
YUMPU automatically turns print PDFs into web optimized ePapers that Google loves.
Architectural Implementation Pilot, Phase 3 Version: 2.0<br />
<strong>Global</strong> <strong>Drought</strong> <strong>Monitoring</strong> and European <strong>Drought</strong><br />
Observatory-Water SBA Engineering Report<br />
Date: 11/Feb/2011<br />
network registry. Such a specialized drought vocabulary or a water ontology would link to<br />
drought indicators and drought and water datasets used in common with <strong>the</strong> European <strong>Drought</strong><br />
Observatory. The Simple Knowledge Organizing System (SKOS) had been used to express this<br />
GEMET data structure, so <strong>the</strong> water ontology, developed in AIP-3, would also be translated into<br />
SKOS data structures and linked to relevant terms in <strong>the</strong> reference <strong>the</strong>sauri as an AIP-4 activity.<br />
5.4.1 Water Ontology-enablement within <strong>the</strong> DAC Semantics<br />
One possible candidate as a foundation water ontology was <strong>the</strong> USA Consortium of<br />
Universities for <strong>the</strong> Advancement of Hydrologic Sciences (CUAHSI) water ontology, version 1.<br />
The CUAHSI water ontology does list water stores of surface and subsurface (soil) water,<br />
<strong>the</strong>reby meeting some of <strong>the</strong> requirements needed in a hydrologic drought indicator. Fugazza<br />
has converted <strong>the</strong> CUAHSI Ontology Web Language (OWL) into SKOS, as an AIP-3<br />
contribution (See AIP-3 Semantics Engineering Report).<br />
5.5 How <strong>the</strong> Euro<strong>GEOSS</strong> Discover Augmentation Component supports semantic<br />
searches<br />
To conclude, <strong>the</strong> Discovery Augmentation Component enables semantics-aware<br />
discovery by matching <strong>the</strong> search patterns entered by <strong>the</strong> end user against a collection of<br />
multilingual, SDI-related <strong>the</strong>sauri: <strong>the</strong>se are controlled vocabularies providing multiple textual<br />
representations for terms and organizing <strong>the</strong>m according to specificity and relatedness. As a<br />
consequence <strong>the</strong> user’s query is first related to a set of language-neutral identifiers (URIs) (like<br />
<strong>the</strong> URIs used for geographic spatial entities, noted above in section 5.2.1.2). These URIs<br />
represent entities in a concept graph that <strong>the</strong> user may navigate for identifying related terms that<br />
are relevant to her search. These data structures are hosted by <strong>the</strong> GENESIS Vocabulary <strong>Service</strong>.<br />
These <strong>the</strong>sauri are provided in <strong>the</strong> Simple Knowledge Organizing System (SKOS)<br />
format, a lightweight ontology for expressing knowledge organization systems (such as<br />
taxonomies, classification schemes etc.), and have been harmonized in <strong>the</strong> context of <strong>the</strong><br />
Euro<strong>GEOSS</strong> project by relating terms from distinct <strong>the</strong>sauri, thus allowing <strong>the</strong> user to move from<br />
one categorization to <strong>the</strong> o<strong>the</strong>r, i.e., one scientific discipline to ano<strong>the</strong>r within a GEO SBA or<br />
from one SBA (water) to ano<strong>the</strong>r SBA (agriculture). Once <strong>the</strong> user has identified an exhaustive<br />
set of terms that are relevant to her query, <strong>the</strong> broker translates <strong>the</strong> corresponding URIs back to a<br />
customizable set of languages and executes multiple queries against <strong>the</strong> catalogs it is federating<br />
(recalling <strong>the</strong> desired datasets).<br />
The Euro<strong>GEOSS</strong> Discovery Augmentation Component (DAC) implements a query<br />
expansion strategy deriving multiple traditional geospatial queries from a single semantic query.<br />
The DAC is able to accept a semantic query and, accessing a configurable set of external<br />
semantic services (e.g. controlled vocabularies, gazetteers, etc.), split it into several geospatial<br />
queries directed to a set of federated traditional/standard services for geospatial resources<br />
discovery. Results are finally combined in a meaningful way and sent back to <strong>the</strong> client.<br />
This framework realizes <strong>the</strong> Separation-of-Concerns pattern assigning specific tasks to<br />
Page 56