Databases Reference
In-Depth Information
Logics) [12] for policy specification. The policy framework is founded on three
atomic concepts defined in OWL DL.
<owl:Class rdf:about="#Action"/>
<owl:Class rdf:about="#Condition"/>
<owl:Class rdf:about="#Resource"/>
Policy actions are Web Services that make the resources available and per-
form manipulations on the resources. Policy conditions are contextual events
such as road topology or location data, and a resource can refer to the spatial
extents of an object such as ”building” with a polygon with a set of points.
The access policies for a client are defined with OWL geospatial access con-
trol ontology, which enables reasoning engine to carry out conflict checks for
possible loopholes. The spatial resources are organized with different levels
of ontologies. First, it has the domain specific ontology, e.g. county ontology
with spatial resources such as school, municipal building, park, etc., as pri-
mary concepts, and instances of these concepts as West Orange High School,
City Government, etc. In addition, each of these concepts refer to the external
upper ontology on the geospatial ontologies, that shows the geospatial related
concepts and their relationships such as ”features” has spatial extent to con-
cepts such as polygon or line, and each polygon consists of a set of coordinates
that form a closed ring. Figure 3 shows the relationships among different types
of ontologies.
Has Spatial Extent
Linear
Ring
Coordinates
Feature
Upper
Geospatial
Ontologies
Polygon
HasExteriorRing
String
g
String
Government
Building
County
Ontology
School
Park
WO Middle
Sh l
Essex
Ontology
Branch Brook
Branch Brook
Park
School
gy
Instances
(Ground
Facts)
Court
West Orange
High School
Newark City
Government
Fig. 3.
County Ontology Hierarchy
