with ontologies. It is necessary to evaluate what
would be the best alternative: creating a new version
of Java2OWL which uses Jena or refactoring the
current code of ContextP-GSD and related projects
to use OWL API. Considering the contribution to
the Semantic Web community, we conclude that
creating a new version of Java2OWL is the best
alternative. It would also allow us to use SPARQL
queries and reasoning features and the various triple
store solutions.
There are still some complex issues related to
OWL, like dealing with multi-inheritance in a less in-
trusive way, dealing with inconsistencies in the ontol-
ogy, and considering open and closed world assump-
tions, that could be better explored as we advance in
working with the tool.
6 CONCLUSIONS AND FUTURE
WORKS
It was presented a qualitative comparison among
some solutions to map application data to OWL rep-
resentation by means of Java Annotations. This facil-
itates the incorporation of semantic features in legacy
systems in a little intrusive way. It also reduces the
programming effort since it eliminates the need to
write code responsible to map specific Java classes to
OWL concepts for every internal operation which in-
volves manipulating application entities. Another ad-
vantage is that such mapping approach allows any de-
veloper to cumulatively construct the ontology TBox
as the mapping becomes more detailed.
Among many researched approaches, there are
two outstanding technologies: Java2OWL and JAOB.
The first one showed to be the most appropriate for
DiSEN’s application scenario, because of its wide
OWL features support and its focus on synchroniza-
tion between application data and OWL. Moreover,
Java2OWL is an ongoing project whereas JAOB is not
being supported.
Although many advantages were encountered in
these approaches, there are still some issues. First,
the mapping does not cover all of the OWL vocabu-
lary yet. Indeed such mapping is not trivial. There-
fore it still needs a lot of improvements. Second,
such approaches only support OWL API, which is not
suitable when it is intended to use SPARQL queries
and/or triple stores. In DiSEN’s case, it becomes
even more serious since there are already many imple-
mented semantic features using Jena instead of OWL
API.
For our case, it is necessary to make a choice:
migrating to OWL API or implementing an exten-
sion of Java2OWL or JAOB to support Jena. The
first one is interesting, however it would be neces-
sary to discard the increasing progress of technolo-
gies based on RDF triples, such as SPARQL and triple
stores. Benchmarks like Berlin SPARQL Bench-
mark (BSBM) (Bizer and Schultz, 2009) are contin-
uously exposing the performance improvement made
on triple stores and SPARQL engines. Though there is
the OWLDB alternative for persistence and querying,
it may not be appropriate to ignore all of the current
work being done on triple stores.
Based on that we conclude that the best choice is
to implement an extension of Java2OWL which sup-
ports Jena. It would allow us to take advantage of
triple-based technologies without losing the possibil-
ity of using OWL API and OWLDB. Furthermore, we
intend to gradually improve such tool in order to ad-
just it for our needs.
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