What is ontology? What do we need to create and maintain it? How can be ontology useful? Here are several links which can help you to answer these questions.

Definitions

http://en.wikipedia.org/wiki/Ontology_(computer_science)

http://www.ksl.stanford.edu/kst/what-is-an-ontology.html

http://www.aaai.org/AITopics/html/ontol.html

Ontology management systems

http://sw-portal.deri.at/papers/deliverables/d17_v01.pdf

http://www-scf.usc.edu/~csci586/project/group3/

http://km.aifb.uni-karlsruhe.de/ws/LLWA/fgml/final/Stojanovic.pdf

http://protege.stanford.edu/

http://www.xml.com/pub/a/2004/07/14/onto.html?

Ontologies in the related projects

The role of semantics in e-government service model verification and
evolution (OntoGov)

http://www.imu.iccs.gr/Papers/C75-SWEG-06-Ontogov.pdf

A Governmental Knowledge-based Platform for Public Sector Online Services
(A platform for the SmartGov project)

Abstract: http://www.smartgov-project.org/index.php?category=viewsummary&langid=eng&dlFileDesc=D71

Full version: http://www.smartgov-project.org/index.php?category=getfile&langid=eng&dlFileDesc=D71