9 Access Control Systems for Geospatial Data and Applications
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individuals that, because of the role they have in the community, need to access common information resources through LBS. Mobile organizations thus consist not only
of enterprises operating on field such as fleet management and resources tracking
but also of health care and leisure organizations, and military and civilian coalitions
created in response to a crisis, for example natural disaster and war. In these organizations, the mobile members are characterized not only by an identity but also by
a functional role. Because of the different activities of the organization’s members,
it is reasonable to consider that LBS (services for short) are requested based on the
roles of individuals and also their position.
The GEO-RBAC model addresses the above issues; it relies on RBAC standard
and, like RBAC, is based on the concept of role. Moreover, it is structured in levels,
referred as Core, Hierarchical, and Constrained GEO-RBAC, respectively. Of these
levels, we describe here the Core level, which constitutes the basic component. For
the additional levels, we refer the readers to [12].
Before proceeding, we introduce the running example that will be used throughout the chapter. Consider an LBS application for a university campus. The campus
consists of various buildings and areas, such as departments, libraries, and recreative
areas, each occupying a position in space. From an organizational point of view, people in the campus can play one or more functions, such as teachers, students, visitors,
and, say, library subscribers. The members of the campus are connected to a wireless
network and equipped with a location-aware PDA by using which they access various LBSs. Assume that John is a student and also a library subscriber. When located
within one of the libraries of the campus, John is presented with various services,
for example the book-loan service to request the loan of a book. Instead, when in a
department, he can request the class timetable.
9.4.1 Overview of the Core Level
By adapting the definition in [13] to our model, we say that Core GEO-RBAC
defines a minimum collection of elements which are required to completely achieve
a GEO-RBAC system. The basic notion is that of spatial role, which describes a
spatially bounded function for a user. Two other concepts, however, are noteworthy: (a) the position model which describes the position of the mobile user; (b)
the notions of role schema and role instance which provide a representation of
the role at two levels, respectively, the intensional and the extensional level. For
the representation of the position of the user and the spatial properties of roles,
we rely on current geospatial standards [16]. In particular, we describe the spatial
objects which are located in the reference space in terms of simple features [16]
(hereinafter, features). Features have an identity, thematic properties, and can be
mapped onto a position in the reference space. A feature is denoted by its identifier. For example, UniMi is the identifier of the spatial object which describes
the properties of a campus and its position. The position of a feature is represented through a geometry which can be of type point, line or polygon, or
recursively a collection of geometries. Further, geometries can be related by different types of relationship. Among them, the reference set of topological relations is
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individuals that, because of the role they have in the community, need to access common information resources through LBS. Mobile organizations thus consist not only
of enterprises operating on field such as fleet management and resources tracking
but also of health care and leisure organizations, and military and civilian coalitions
created in response to a crisis, for example natural disaster and war. In these organizations, the mobile members are characterized not only by an identity but also by
a functional role. Because of the different activities of the organization’s members,
it is reasonable to consider that LBS (services for short) are requested based on the
roles of individuals and also their position.
The GEO-RBAC model addresses the above issues; it relies on RBAC standard
and, like RBAC, is based on the concept of role. Moreover, it is structured in levels,
referred as Core, Hierarchical, and Constrained GEO-RBAC, respectively. Of these
levels, we describe here the Core level, which constitutes the basic component. For
the additional levels, we refer the readers to [12].
Before proceeding, we introduce the running example that will be used throughout the chapter. Consider an LBS application for a university campus. The campus
consists of various buildings and areas, such as departments, libraries, and recreative
areas, each occupying a position in space. From an organizational point of view, people in the campus can play one or more functions, such as teachers, students, visitors,
and, say, library subscribers. The members of the campus are connected to a wireless
network and equipped with a location-aware PDA by using which they access various LBSs. Assume that John is a student and also a library subscriber. When located
within one of the libraries of the campus, John is presented with various services,
for example the book-loan service to request the loan of a book. Instead, when in a
department, he can request the class timetable.
9.4.1 Overview of the Core Level
By adapting the definition in [13] to our model, we say that Core GEO-RBAC
defines a minimum collection of elements which are required to completely achieve
a GEO-RBAC system. The basic notion is that of spatial role, which describes a
spatially bounded function for a user. Two other concepts, however, are noteworthy: (a) the position model which describes the position of the mobile user; (b)
the notions of role schema and role instance which provide a representation of
the role at two levels, respectively, the intensional and the extensional level. For
the representation of the position of the user and the spatial properties of roles,
we rely on current geospatial standards [16]. In particular, we describe the spatial
objects which are located in the reference space in terms of simple features [16]
(hereinafter, features). Features have an identity, thematic properties, and can be
mapped onto a position in the reference space. A feature is denoted by its identifier. For example, UniMi is the identifier of the spatial object which describes
the properties of a campus and its position. The position of a feature is represented through a geometry which can be of type point, line or polygon, or
recursively a collection of geometries. Further, geometries can be related by different types of relationship. Among them, the reference set of topological relations is