Protege inconsistent ontology ambiguous explanation

Question

I have a class Course and a data property courseCode on the domain Course with range xsd:string .

I added an individual, a Course named "Databases". I also wanted to add the data property assertion courceCode with a value of "DAT475" and a type of xsd:string . But after doing that I get this error:

What does this mean? What did I do wrong?

Edit: The file I'm working on is using turtle syntax.

Answer 1

You have a plain literal (the presence of an @en language tag separates a plain literal from a string literal) as filler for a property whose range is defined as xsd:string (ie, limited to string literals only).

It's a bit counterintuitive, but the problem is that plain string literals and strings are not in the same datatype.