Hmm. Well, as all first quick and dirty drafts in unfamiliar territory, this one has to go down the drain. I'll leave it up anyway in case you want to play with it.
I've just discovered an ISO 19103 ontology, which is great: they have the basics laid out for units of time and space (great for spells and other things) and it's a good example for me to follow and figure things out. It also has provisions for records and data dictionaries, a definite plus to manage all the objects that will be in there.
And I've looked at SWRL, and it seems it's a rather complete rule language with conditionals and arithmetic. So I still believe that a custom rule language is not the way to go (IMVHO of course).
Andargor