If you regularly run into words like "ontology" and acronyms like OWL, then you'll be pleased to hear that Protege 4.0 (news, site) has been released.

Those who aren't deeply involved in the semantic web may not quite run to learn more, but semantic web technologies are coming faster than you think. It's a good idea to pay at least some attention.

What is Protege?

Protege is a free open source ontology editor built for working with the Java API for the W3C Web Ontology Language, or OWL.

If you aren't familiar with ontologies, they define the terms used to describe and represent an area of knowledge, typically by describing the relationships between the terms. Given the amount of data within an ontology, some ability to graphically edit and navigate the terms and relationships makes the task much easier on human eyes.

Protege in general offers a wide range of features for viewing, cloning, importing, and otherwise working with these masses of interlinked data.

What's New with Protege 4.0?

The Protege 4.0 release offers a number of new features. For one thing, it supports the in progress OWL 2.0 specification, which is now stabilizing as it approaches approval. This version also has an important technology more heavily baked in than it used to be: a pair of OWL Description Logic (DL) reasoners.

OWL DL is one of three levels of OWL that you can choose from if you decide to make use of the ontology language. This level described in the W3C document "OWL Web Ontology Language Guide" as supporting "those users who want the maximum expressiveness without losing computational completeness (all entailments are guaranteed to be computed) and decidability (all computations will finish in finite time) of reasoning systems."

Learning Opportunities

Protege components that handle the complex interlinks of OWL DL are called reasoners. Semantic reasoners look over a collection of stated facts and then work out the resulting logic. The two OWL DL reasoners included with Protege 4.0 by default, Fact++ and Pellet, are now directly connected to Protege's internals in memory. This connection should speed up performance, given the amount of reasoning required to process an ontology.

Other new features include:

  • Support for editing multiple ontologies
  • Global configuration setting storage
  • Plugin framework extended to define all user interface elements including tabs, views and menus
  • Can import from common folders, user repositories or the web
  • Now uses the industry-standard OSGi plugin/module framework
  • Menu drag and drop user interface elements

The Protege 4.0 OWL editor with a pizza ontology loaded, American pizza featured.

Which Version Should You Use?

Protege 3.x and Protege 4.0 offer somewhat different feature sets. The Protege team offers a migration page to help you decide whether you want to stay with the previous version or upgrade to the new one.

Even if you aren't an ontology buff, Protege 4.0 comes with easy access to a number of existing ontologies. You can learn a lot about how these frameworks are put together by taking a look a them here.