This looks very interesting. Is there any possibility that you could offer an option to switch the direction of the links, i.e. <?Child::Father::Father::Name> ? That's personally a little more intuitive to me.
Topic on Extension talk:Semantic Expressiveness
That would be what programmers might be used to. But perhaps not authors who are not into programming. So for example <?Name> , I find it more consistent with <?Name::Site> because the property will always be the first thing you write. Also, the :: will read like an of (at least in English language this makes sense, not sure about some other languages though). It might be an option to make it configurable at some point.
Are there really some good arguments against this syntax? I have discussed this before and besides the point that some programming languages might do it the other way around, I didn't find any.
I prefer "the Child's Father's Father's Name". I imagine typing the code out and saying in my head something like that... it's just easier for me to walk forward down that path than backward.
Of course, it is just a matter of personal preference. I can't think of any objective reason to pick one over the other. Perhaps it might be easier for people writing right-to-left languages to think of it in one way than the other.
Well, one (gentle) reason is that SMW already does relations from left-to-right.