SEKE 2012 Proceedings - Knowledge Systems Institute

in the vicinity of the display. The information about whom
is in the vicinity of the display is acquired by the detection
of their devices through a symbiotic relation among them.
2. Related Work
Due to the importance of context for Pervasive Computing
as a whole, many works has been carried out with the
intention of represent the contextual information from the
environment. In a general way, these works can be grouped
into two categories: (i) the comprehensive works - where
the authors try to gather the maximum of information for
represent context, but always according with the scope of
some application being developed [6, 7, 8, 9]; (ii) the synthetic
works - which try to find a minimal set of information
that can be used in most applications [10, 11, 12].
The problem in adopt these works in Pervasive Advertising
is that when the developer adopt a comprehensive
model, add a new concept, or a task ontology, is not possible,
once there is a strong coupling between the existent
classes. Still, if the developer tries to adopt a work that uses
the synthetic approach, the minimal modeling will force
him to extend the solution for contemplate each kind of
product that will be announced, and eventually, when many
concepts are added to the model, the developer will find the
same problem from comprehensive approach.
The main problem with these works is that they cant
be applied to the Pervasive Advertising domain, and adapt
them to this domain is a hard task due to the high level of
coupling of the information. We also detach that still there
are not a comprehensive model created for the Pervasive
Advertising [4], which be able to represent specif information
of this domain such as the target audience, and the message
of the ad.
3. The Context Model
To be aware of context is a key concept in order to effectively
develop applications in the scope of pervasive computing.
A good modeling formalism reduces the complexity
of developing context-aware applications by improving
their maintainability and evolvability. Considering that the
growing trend of use the multiagent approach for implement
Pervasive Advertising systems, the need of built-in semantics
and expressiveness and the need of computational guarantee,
we decided to adopt OWL DL Ontologies for modeling
the contextual information.
The conception of a model for Pervasive Advertising is
not an easy task. Mainly because (i) this model must be
comprehensive, in order to address the different needs of
contextual information of applications; (ii) this model must
be loosely coupled, in order to be extensible, in other words,
the incorporation of new concepts still absent shall be easy.
Notice that there is a trade off between the need of low coupling
and comprehensiveness. Once, raising the level of
comprehensiveness increases the coupling, and vice-versa.
To solve this impasse, we did not try to avoid coupling, it
is impossible, but we change the way the coupling occurs to
make it weaker. The key to achieve the result is the association
of the contextual information with the entities capable
of provide these information. These entities are the users
and the devices, once they are the only entities capable of
produce information.
After identified the sources, it is possible to associate
other concepts to them. In this way, the coupling with these
entities is not a problem anymore, once the information
about them are necessary for any application that uses context
in Pervasive Computing paradigm. Following this line
of thought, our model was created using a gradual approach,
and is divided into three layers, they are: the Kernel, Pervasive,
and Advertising layers following described.
3.1. Kernel Layer
In this layer are represented the entities capable of provide
information in scope of Pervasive Computing, they are
the User and Device. The Figure 1 (yellow boxes) illustrates
how the context can be represented in terms of users
and devices. It is also possible to notice in this figure that
a user can holds many devices. In this layer there is yet the
representation of location, once this information is directly
associated to the user and device.
It is also common to think in the environment as a source
of information. But, actually the environment is only a representation
of a location, a place. In this way the information
about the environment can be obtained through the
devices that are in a specific location. This means that all
the information can be obtained either from the user or the
device. For example, the information about the gender of a
person can be directly provided by him or herself. Or the information
about the temperature of a place can be obtained
by a sensor (device).
Other aspect is the specification of the Device Profile
that can be a hardware or a software profile. The Hardware
Profile describes specific characteristics of a device,
such as memory and processor power, battery level, and
screen size. The Software Profile follows the same line of
though, including the characteristics of software of a device
like browser support and characteristics.
3.2. Pervasive Layer
The Pervasive layer gathers the information that can be
relevant for most applications from different domains. That
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