Ontology Files

Rather than expecting someone to know specific parameter codes for successfully querying a number of data sources one by one, a concept ontology is used. These ontologies that are coded in OWL, a specialized language for ontologies that is based on XML. The OWL Editor Protégé was used to create them. In addition, one of the main reasons to use OWL for encoding, besides the semantic richness its rules allow for, is that that one can deploy a parser of which several are available for free. These are codes that can also be incorporated into JAVA or .NET applications. This represents a significant time savings in terms of coding and functionality.

The file search.owl is the backbone of the search ontology. However, it does little more than include all sub-ontologies to form a single file, as shown in the text box below. This file is accessed by the search engine when resolving the keyword search and drilling down to the leaf levels to find the ConceptCodes that lead to the variable codes in the ODM. While most entries into the ontologies are straightforward class definitions without any domain or range restrictions, some of the classes actually do have restrictions placed on them. These restrictions, mostly “single parent” restrictions, are necessary because the class itself does not have a unique definition and could be placed elsewhere in the ontology. A restriction to a certain parent class ensures that a given subclass cannot be confused (or moved) to any other class but the identified parent class in effect making it a unique class with a unique location inside the ontology.

<?xml version="1.0"?>
<rdf:RDF
xmlns:wq‐ext="http://www.cuahsi.org/waterquality‐extended#"
xmlns:nwis="http://www.cuahsi.org/nwis#"
xmlns:rdfs="http://www.w3.org/2000/01/rdf‐schema#"
xmlns:owl="http://www.w3.org/2002/07/owl#"
xmlns:met="http://www.cuahsi.org/meteorology#"
xmlns:nav="http://www.cuahsi.org/navigation#"
xmlns:wq‐syn="http://www.cuahsi.org/waterquality‐syn#"
xmlns:wq="http://www.cuahsi.org/waterquality#"
xmlns:flow="http://www.cuahsi.org/flow#"
xmlns:epastoret="http://www.cuahsi.org/epastoret#"
xmlns:rdf="http://www.w3.org/1999/02/22‐rdf‐syntax‐ns#"
xmlns:met‐ext="http://www.cuahsi.org/meteorology‐extended#"
xmlns:met‐syn="http://www.cuahsi.org/meteorology‐syn#"
xmlns:flow‐ext="http://www.cuahsi.org/flow‐extended#"
xmlns:flow‐syn="http://www.cuahsi.org/flow‐syn#"
xmlns="http://www.cuahsi.org/search#"
xml:base="http://www.cuahsi.org/search">
<owl:Ontology rdf:about="">
<owl:imports rdf:resource="http://hydroseek.org/search/ontology/meteorology.owl"/>
<owl:imports rdf:resource="http://hydroseek.org/search/ontology/flow‐syn.owl"/>
<owl:imports rdf:resource="http://hydroseek.org/search/ontology/meteorology‐syn.owl"/>
<owl:imports rdf:resource="http://hydroseek.org/search/ontology/waterquality‐syn.owl"/>
<owl:imports rdf:resource="http://hydroseek.org/search/ontology/waterquality‐extended.owl"/>
<owl:imports rdf:resource="http://hydroseek.org/search/ontology/flow.owl"/>
<owl:imports rdf:resource="http://hydroseek.org/search/ontology/waterquality.owl"/>
<owl:imports rdf:resource="http://hydroseek.org/search/ontology/navigation.owl"/>
<owl:imports rdf:resource="http://hydroseek.org/search/ontology/flow‐extended.owl"/>
<owl:imports rdf:resource="http://hydroseek.org/search/ontology/meteorology‐extended.owl"/>
</owl:Ontology>
</rdf:RDF>

Contents of the search.owl File