![](bg2.png)
News@hand, a hybrid recommender system for
ontology-based personalized and context-aware rec-
ommendations of news items was presented in (Can-
tador et al., 2008). The news items are automatically
and periodically retrieved via RSS feeds and anno-
tated with semantic concepts from system domain on-
tologies. During an interaction with the user a set of
weighted concepts from the domain ontologies is col-
lected. A user context is represented by this set. The
importance of concepts fades away with the time by a
decay factor. This helps to keep the user context up to
date. Existing relations between concepts in the on-
tologies are used to find semantic paths linking pref-
erences to context.
A context-aware system which recommends Web
services to users was described in (Rodriguez et al.,
2013). The main idea is using a multi-dimensional
ontology model to describe Web services, a user
context and an application domain. The multi-
dimensional ontology model consists of a three inde-
pendent ontologies: a user context ontology, a Web
service ontology and an application domain ontology,
which are combined into one ontology by some re-
lations between concepts from different ontologies.
Data from a WSDL file for a Web service are auto-
matically added into the Web service ontology during
the registration process. The user must specify the
name, birth date, sex and occupation to build his pro-
file. The user context ontology consists of those pa-
rameters and a list of interests. Every item of the list
has a level of interest property, which is used to as-
sign a weight to the item during the recommendation
process.
5 METHODOLOGY
In this section we describe an idea of a contextual ap-
proach to an ontological user profile (Subsection 5.2).
First, we need to define the contextualontology which
is done in Subsecion 5.1. The general architecture of
the proposed system is presented in Subsection 5.3.
A description of planned experiments and future re-
search close this section.
5.1 Structured-interpretation Model
Contextual ontology introduced in (Goczyła et al.,
2007) enables us to model different situations in
which a user could find himself as a set of ontological
modules. As an ontology we mean here a Description
Logics (DL) ontology which consists of a terminol-
ogy (TBox) and a world description (ABox). As a
context we understand a part of TBox defined by val-
T
A
A A
A
A
A A
A
A
T T
T
T
1
1
2
2
3
3
4
4
5
5 6 7 8
specializes
context
contextinstance
instance-of
is-aggregated-by
9
Figure 1: Structured-Interpretation Model (from (Goczyła
et al., 2007)).
ues of a set of contextual parameters. The contexts are
arranged in an inheritance hierarchy. More special-
ized terminologies may ,,see” more general ones, but
more general terminologies are unaware of the exis-
tence of more specialized ones. To deal with possible
different assertional parts of the knowledge base we
can create many ABoxes for one terminology. These
ABoxes are called context instances. To allow for
a flow of conclusions between context instances, the
context instances are connected by relation of aggre-
gation. This approach to modularization, described in
details in (Goczyła et al., 2012), is called Structured-
Interpretation Model (SIM) and is illustrated in Fig. 1.
To explain how the contextual ontology works we
use a simple example taken from (Waloszek, 2010).
Let assume that an ontology consists of two contexts
(TBoxes) and three context instances (ABoxes). Con-
text T
1
provides concept Can
resuscitate from which
concept Doctor inherits. Doctor is a concept pro-
vided in the terminology of context T
2
. Context in-
stances A
2
and A
3
describe a situation of an individ-
ual called john
doe from different points of view: he
is a doctor in Poland but legally he is not a doctor
in United Kingdom. Assertions Doctor( john
doe)
and ¬Doctor( john doe) are contradictory, neverthe-
less the ontology is consistent. It is because the con-
cept Doctor is defined below the context instance A
1
which aggregates context instances A
2
and A
3
. The
concept Can
resuscitate is immanent for the context
T
2
because it is defined on the level of the context in-
stance A
1
. Therefore the conclusions reflecting the
fact that John Doe can resuscitate can flow between
the two contexts (in Poland and in the United King-
dom). This example is shown in Fig. 2.
Another example is shown in Fig. 3. Here we have
three contexts: T
1
that describes general notions of
Woman and Man, T
2
that specializes T
1
towards de-
scription of voices in a choir, and T
3
that also spe-
cializes T
1
but towards description of social relations.
IC3K2014-DoctoralConsortium
84