SEKE 2012 Proceedings - Knowledge Systems Institute

Figure 1. UML view of the model. The yellow boxes represent the Kernel layer and the device
properties; the green box represents the Pervasive layer; and the red boxes represent the Advertising
layer the advertising properties. This model view is simplified containing only the most important
classes and attributes.
is, we believe that is possible to model the contextual information
according to aspects that are useful for many application
domains instead of focuses in specific domains of
applications. For example, the services available in the location
is an information useful for applications of different
domains.
Following this point of view, we can think that is possible
to classify the context in classes, as follows:
Group of Users: People usually establish relationships
with other people, either by sharing the same location
(e.g., workplace, city) or because they have common
interests. In this work, a group of users consists of
people who have something in common such as location,
and interests. Through this concept is yet possible
to deal with the concept of social networking. Social
Network is a form of representation of emotional
or professional relationships of human beings among
themselves or among their groups of mutual interests.
The same idea can be applied to the devices, in which
a device can form a group with other devices that have
characteristics in common. For example, a device can
form a group with the devices that are accessible to a
particular user or with the devices needed to supply a
particular service.
Service: in a pervasive environment, it is common that devices
act as services providers. This service provision
is related to service-oriented architecture (SOA). By
focusing on functionality, the SOA architecture allows
heterogeneous applications can establish relations between
them. Therefore, it is important for a great
number of applications executing in pervasive environments
be aware of the services that each of the available
devices provides.
Sensor and Actuator: these are special kinds of devices,
and their representation is useful when it is necessary
to deal with the idea of environment. In this representation
the environment is a kind of derivate information,
which can be obtained when combined with the
location.
Time and Period: the notion of time is useful for applications
once it introduces the concept of period. This is
yet useful yet to establish a chronological order of the
facts, a history.
Activity: the activity of a user is an information very useful
for application that intend to deal with personalization
of services.
In the Figure 1 (green box) these concepts and their relationships
are represented. Notice that it is possible to exist
others classes useful for pervasive applications, such as
Event. However, in practical terms it is impossible to cover
all the classes, for this reason we did not make an exhaustive
list. We decide to focuses on the most useful classes, once
the incorporation of new classes can be easily done by extending
the model. What make this model easy of extending
is the way the classes are coupled, notice that none of the
classes on kernel layer make reference to the others layers.
This means that a modification in the Pervasive layer does
not affect the kernel layer.
3.3. Advertising Layer
The advertising layer was created to contemplate
specifics characteristics of Pervasive Advertising. In Figure
1 (red box) the main concepts related with the advertise-
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