A Software Engineering Framework for Context-Aware Service-Based Processes in Pervasive Environments - Advanced Design Approaches to Emerging Software Systems - page 109

Table 1. Feature Type Relations

needs to use context information, s/he reads the
XML file representing the context features the
context manager is able to deliver to understand the
context semantics. Then s/he is able to configure
the feature model and use the context manage-
ment infrastructure services to get the necessary
context information.
On the other hand, ontologies are a very
promising instrument for modeling contextual
information due to their high and formal expres-
siveness and the possibilities for applying ontology
reasoning techniques. Thus, we focus on context
management employing ontologies as the under-
lying technology. Several successful efforts have
been developed in order to support context-aware
applications through ontology-based middlewares
and models for describing context information.
Common to most of the existing approaches the
usage of ontologies (e.g. using OWL) to describe
the concepts and properties defining context in-
formation in the relevant domain: context types
correspond to classes defined in the ontology.
RDF is implicitly used as the common, standard
language to express classes and individuals (i.e.
context types and their instances). Obviously the
reasoning capabilities of the ontology are of cru-

cial importance to context-aware applications for
context knowledge representation and reasoning.
Although a feature model can represent context
commonalities and variabilities in a very concise
taxonomic form, features in a feature model are
merely symbols. Mapping features to the context
ontology gives them semantics. In the follow-
ing section we describe the proposed approach
of mapping the feature model to the ontology
context model.

Annotated Context Model

An overview of the proposed approach is shown
in Figure 3. A context model family is represented
by the context feature model and the ontology-
based context model (OCM). The elements of
OCM namely the context primitives may be
annotated using existence conditions (ECs) and
meta-statements (MSs). These annotations are
defined in terms of features and feature attributes
from the feature model, and can be evaluated with
respect to a feature configuration. An EC attached
to a context primitive indicates whether the primi-
tive should exist in or should be removed from a
context product. MS is mainly used to modify or