Context Description
We conceive context aware is an interactive model between learners and services, thus, we need to address the
context description of learners and services. We have developed two types of context ontology for describing
learners and services, they are learner ontology and service ontology (Yang, et. al. 2005).The interactive model
is enacted by a semantic matchmaker that can perform semantic reasoning for context oriented service discovery
and access based on the two context ontology.
We have utilized Protégé (http://protege.stanford.edu/) to build the learner ontology and service ontology as
shown in Figure 1.
The major difference between the learner ontology and service ontology are their profiles. The learner ontology
contains learner profiles such as personnel profile, accessibility and preferences, calendar profile, social profile,
and location profile; The service ontology contains service profile such as input, output, pre-condition, and effect
of service execution.
In addition to profiles, both learner ontology and service ontology contains surrounding context such as quality
of learning service, environment profile, and device capability profile. Quality of learning services profiles
(QoLS) contain functionally and non-functional QoLS constraints; Functional QoLS constraints can be described
by network bandwidth and response time; non-functional QoLS constraints can be described by reliability,
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availability, and cost. Environment profile contains network channel constraints and situated location
constraints; Network channel constraints can be used to describe types of channels such as wired or wireless;
situation constraints can be used to describe requester situated environments such as in a meeting, reading,
walking, or driving. Device profile contains the device’s hardware and software constraints. Various devices
such as PDA and mobile phones are equipped with different hardware and software constraints. Hardware
constraints can be used to describe device hardware capabilities such as platform, CPU speed, memory size,
screen size and resolution. Software constraints can be used to describe device software capabilities such as
operating system, browser, playable media type and resolution.