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12.4 Acquiring Domain Knowledge 291

knowledge-base editor available atprotege.stanford.edu. It is writ-

ten in Java, and can be used to create customized knowledge-based ap-

plications. It was not originally developed for OWL, but it has an OWL

“plug-in” called ezOWL (ezOWL 2004)that allows one to edit OWL on-

tologies. Two of the authors of Protégé have written a nice article on

ontology development using Protégé, called “Ontology 101” (Noy and

McGuinness 2001).

6. Computer-aided software engineering (CASE) tool. Ontologies are a
   form of software and it is possible to use software engineering tools and
   techniques to build ontologies (Baclawski 2003). There are differences be-
   tween ordinary software development and ontology development, but
   it is possible to reconcile these differences (Baclawski et al. 2001; Kogut
   et al. 2002). The DAML UML Enhanced Tool (DUET) translates from the
   Unified Modeling Language (UML), the standard modeling language for
   software, to DAML, the predecessor of OWL (DUET 2002). If one is ac-
   customed to using CASE tools, then it is convenient to use a CASE tool.
   However, if one has no experience with CASE tools, it is better to use a
   tool specifically designed for ontology development.

Summary

The following are the main groups of approaches and tools for ontology de-

velopment:

• No explicit ontology or tool


• Automatic generation of the ontology from examples


• XML editor

•RDFeditor

•OWLeditor

• CASE tool adapted for ontology development

12.4 Acquiring Domain Knowledge

All ontologies are ultimately based on “domain knowledge.” Acquiring and

formalizing knowledge about the domain is necessary for ontologies that are