Databases Reference
In-Depth Information
one approach called Geo-RBAC where the map vector data and user's posi-
tions are considered to protect resources in location aware applications. Some
examples of access policies that can be supported under this model include:
•
P1: Only the environmental scientists currently making observations in
the river within the New Jersey Meadowlands area can enter the observed
fish counts into the database.
•
P2: A surveyor working on a street in Newark can change the data on the
illegal waste deposits in the region where he is located.
In Geo-RBAC, the protected resources are mostly vector data that are
modeled with geometric shapes and associated locations.
Geometric Model and Spatially aware Objects
An object on the Earth is represented by a geometric shape, a point, a line or
a polygon. Each geometric object is tied to the Earth coordinates. A point de-
scribes a single location, a line represents an ordered sequence of points, and a
polygon is an ordered sequence of closed lines. GEO is the set of all geometrics
contained in a reference space called Minimum Bounding Box (MBB).
Objects to be protected consists of data about entities of the real world
that may occupy a position. These entities are called features. Features rep-
resent the spatial and non-spatial attributes. Spatial features have name and
location, i.e. geometry, while non-spatial features are not associated with any
location. An example of a feature is
Newark
which can be associated with a
polygon or point geometry. The features are can have feature types such as
Road, Town, Lake, Car
.
Spatial Role
A spatial role is defined as a pair
where
r
is a role name and
e
is the
spatial extent determined by the boundaries of the space in which the role
can be assumed by the user. Role extent can be a feature. A role
surveyor
can be associated to different extents, resulting in different spatial roles, e.g.
r, e
surveyor, city of Rome
,and
surveyor, city of Newark
, are two spatial roles.
Positional Model
The actual user position that can change in time is modeled with either a
real
position
, that is actual geometry such as a point or a polygon, and/or a
logical
position
, i.e. spatial feature (such as city). There is a one-to-many
mapping
function
that can map the real position to logical positions.
