To throw further darkness on this discussion, it is
clear that individual words are not copyrightable, but a whole novel is.
Similarly, I would assume that an individual classification statement such as
"Socrates is a man" or "All men are mortal" would be uncopyrightable, however
that a complex system would be. Further, there is a distinction between the
publisher's copyright on the form of a text, but that is separate from the
author's copyright of the text itself - for example, Shakespeare is out of
copyright, but that does not give me the right to photocopy a recently published
edition of a Shakespeare play.
The question therefore is, at what point does a
classification system become copyrightable? (in the sense of an author's
copyright, rather than a publisher's copyright) Or better, at what point
does a collection of classification statements become a copyrightable system?
And at what point does the overlap of one system with another become an
infringement of copyright? This question may become more vexed by the way that
at some level, the many individual statements of classification will be
statements of the obvious.
A further complication is that in an ontology, one
defines the set of differentia between classes (the properties of the class) on
a class by class basis, and therefore one can infer the
hierarchy without explicitly stating it. It would be an
interesting discussion as to whether an inferred classification system which is
identical to an explicit classification system are comparable in copyright