Protege4ErrorClasses
Error Classes
You may open an ontology and find subclasses of owl:Thing named Error1, Error2, etc. These classes are created by the OWL API as of version 3.2.2. Your document is a valid RDF document, but it is not a valid OWL document. Your document will be parsed and loaded, and Protégé 4 still displays your asserted class hierarchy (subclass assertions are part of RDFS, not OWL). However, you will probably encounter errors if you use a reasoner.
As of version 4.1 beta (build 218), Protégé 4 reports the error only through its GUI. No diagnostic message is displayed in the console. If you save your ontology, it will contain references to the Error classes.
When the OWL API detects an error, it provides some clue about the cause by asserting an equivalence between an Errori class and an expression involving offending entities. In other words, you can diagnose an error by selecting one of the Errori classes in a class hierarchy window and clicking the Class Usage display. Examining the displayed usages will help you understand your error.
