Databases Reference
In-Depth Information
owners. Moreover, these policies for secure sharing should be properly man-
aged so that the right policy can be eciently located and policy inferences
can be easily performed.
In this chapter, we review the access control models presented in the areas
of geospatial data maintained by stand alone traditional sources as well as
that obtained via geospatial Web services. When making access control deci-
sions, the access control models typically consider the characteristics of the
geospatial data (object) and the location of the user (subject). This is because,
the security and privacy policies are often based on the object's contents and
the subject's location. For instance, access control policies may be specified
based on the geospatial object characteristics such as the geographic coverage
(area or extent), the thematic content within the area, the zoom-levels to a
particular location, the temporal nature of the objects or the requesters, as
well as the location of the requester and his/her roles within the area and
temporal period. Specifically, we review the access control models for geospa-
tial data objects such as satellite images and vector data, and a geospatial
role-based access control model for controlling access to resources depending
on the user's geospatial context as in location-based services, and an access
control model for the semantic geospatial Web services.
This chapter is organized as follows. In section 2, we present the geospatial
object data characteristics and models. In section 3 we discuss different fla-
vors of geospatial access control models. Specifically, in section 3.1, we discuss
the geospatial data authorization model presented in [8, 3, 4] where an access
request for geospatial objects is controlled by both geotemporal characteris-
tics of requested object and the user's geotemporal context. In section 3.2,
we present the Geo-RBAC model [7, 11], that provides access control based
on the geospatial roles of the user. Similarly, in section 3.3, we review the
location-based conditional access model to control the mobile user's resource
access, when the user location service is not always precise and sometimes
intermittent. In section 3.4, we discuss the geospatial Web services access
control model. Finally, in section 4, we provide conclusions and an insight
into future research directions in this area.
2 Geospatial Data Models
Geospatial data can be organized in different ways. The vector and raster
models are two principal spatial data organization scheme. The vector model
uses the geometry, such as points, lines, polygons, while the raster model uses
cells or pixels as spatial units.
2.1 Vector data
The vector model represents geospatial data with two components: spatial
attributes and non-spatial attributes. First, the spatial attributes indicate the
