Ontology is a hierarchical structure of knowledge about entities
which subcategorizing entities according to their essential (or at least
relevant and/or cognitive) qualities. Entities can have subcategories
(subclasses or up classes), or different names (alternative words) and
restrictions (entities with specific characteristics). This paper proposes
using ontologies for the purposes of searching and viewing information
in the Web directory, and describes the application that is capable
of using ontologies to get conclusions from the input data on the more
Today, search engines mostly use search indices to find the
occurrances of the words the users enter in the query, but the meaning
of such words is usually unattended. Results differ from users' wishes,
and can often be meaningless. The goal of this work is to create ontology
and an application that is able to search that ontology and view results
for WWW.HR Web directory users. Ontology is created using the Ontology
Web Language (OWL) .
3. Creating the ontology
Creating the ontology may be a complex job because there is
no automated process to do it. Final results depend on the creator's
knowledge. However, the process of creation could be split into three
simpler subprocesses: consideration about domain, planning the domain
and finally, writing the ontology.
Consideration about the domain is the first step in ontology creation,
involving decisions like what will be part of ontology and what should
be omitted. Already existing categorization of the WWW.HR Web direcotry
was used in order to complete this step. Planning the ontology is the
most difficult and demanding task. This step requires consultation with
relevant sources of information (like current subchategorization of
the Web directory or analysis of the most popular words users use to
search the directory). Since all required knowledge about the domain
cannot be extracted from such sources, parts of the knowledge must come
from the creator of the ontology, whose knowledge is used to synthesize
knowledge from many different sources. After the process, the ontology
can be defined in OWL.
4. Application creation
The application was coded in Perl (Practical Extraction and Report Language)
. If the regular search yielded insufficient number of relevant results,
the application may consult ontology and extract knowledge about user's
query. That knowledge is contained in the subclasses of the queried
word, alternative words or synonyms, up classes and possible restrictions.
Subclasses are words that have the meaning (albeit partially) similar
to the query, so searching with subclasses is still similar like searching
with the original class. Alternative words are usually synonyms or words
that come from other languages. Restrictions are used if queries have
5. Results and discussion
Three types of tests were conducted. In the first test, the
directory was searched along with alternative words for user's query.
In the second test all subclasses were included. In the third test,
we used restrictions. First two tests showed more results than standard
search, and the third test showed the opposite, just as it was expected.
It is important to search along with alternative words because in most
languages one word usually has several other forms. Using the ontologies,
less common words can be included in input, such as:
- words that have synonyms that are used almost with the same frequency
as the original word,
- words that come from foreign language but are used in Croatian
language almost as frequently as the original words,
- one word may be used for many other words although they are just
similar words and not synonyms,
- words may have synonyms used much more frequently than the original
Searching with all subclasses included yielded more results then standard
search. Searching for query "car transport" with subclasses
like "bus transport" or "stations" resulted in 56
matches, as opposed to 3, when searching only using query "car
transport". Searching for query „historical monuments" yielded
only 1 result, but with subclasses like „church" and „castle"
included, it yielded 50 results.
Searching with restrictions resulted in less matches because of existing
specific requirements (like location or part), so only pages matching
those requirements were taken into account. Example would be for the
query „airport" which yielded 9 results, but ontology found restriction
for location (cities Zagreb, Zadar, Split), so the number of results
could be much smaller.
In this paper we propose using ontologies for the purpose of
searching Web directory like www.hr. Ontology in the domain of "tourism"
was devised, and application capable of handling it created and tested.
The results show important improvements in regards to the number of
matching results returned to user queries.
 World Wide Web Consortium: URL: http://www.w3c.org/2001/sw/WebOnt/
 Comprehensive Perl Archive Network, URL: http://www.cpan.org/
 Roger L. Costello, David B. Jacobs, OWL Web Ontology Language, tutorial,
The MITRE Corporation, 2003. URL :http://www.xfront.com/
 Đurđica Težak, Pretraživanje informacija na Internetu: priručnik
s vježbama, Hrvatska sveučilišna naklada, Zagreb. 2002.
 Andrijana Prskalo, WWW tražilica prilagođena hrvatskom jeziku, Diplomski
rad br. 2186, Fakultet elektrotehnike i računarstva, Zagreb, 1997.
Damir Jurić graduated from the Department
of Telecommunications, Faculty of Electrical Engineering and Computing,
University of Zagreb in June 2004. His research interests include web
ontology and semantic web and his hobby is literature. He is currently
working as an assistant at the Department of Electrical Engineering
Maja Matijašević received her B.Sc.
(1990), M.Sc. (1994), and Ph.D. (1998) degrees in Electrical Engineering
from the University of Zagreb, Croatia, and the M.Sc. in Computer Engineering
(1997) from the University of Louisiana at Lafayette, LA, USA. Since
1991 she has been affiliated with the Department of Telecommunications,
Faculty of Electrical Engineering and Computing, University of Zagreb,
Croatia, where she currently holds an assistant professor position.
Her main research interests include computer and telecommunication networks,
multimedia, and virtual reality.
Gordan Gledecis a research assistant
at the Department of Telecommunications, Faculty of Electrical Engineering
and Computing, University of Zagreb. He received his B. Sc., M.Sc. and
Ph.D. degrees at the Department of Telecommunications in 1996, 2000.
and 2004, respectively. The title of his PhD thesis was "Metrics
for Web Site Usability Evaluation". His main interests include
Internet and Web technologies and UNIX administration. He has been an
associate at the WWW.HR project since July 1997, and project leader