On Mon, Mar 2, 2020 at 3:27 AM Alexander Gabriel <[email protected]> wrote:
> > > So what happens is the pattern matcher fills the blanks according to what > it > ... according to what it can find in the current atomspace. If nothing can be found, it returns the empty set. > Yes, that doesn't scale to what I intend to do. > I'd like to know why you think that. (what you are trying to do). I'm interested in understanding and solving scaling problems. > >> Ah, it's a completely different query, one where the backward chainer >> tries to find assignments of the free variables of a closed term. >> > > This was unclear to me, so let me clarify, (... and Nil should correct me where I'm wrong.) Suppose that the pattern matcher finds zero solutions to the original query -- there is no combination of human/picker/place1/origin/destination in the *current* atomspace that satisfies that pattern. In this case, the backward chainer then examines the set of rules that it has, to determine, if possible, whether there is a sequence of deductions (a sequence of rule applications) that provide suitable Atoms that allow your pattern to be satisfied. For example, the current AtomSpace might not contain any humans at all, but perhaps there is a way to infer that someone is human. Or a better example: there is no (Evaluation (Predicate "leads to") origin destination) but perhaps the backward chainer can find a sequence of multiple steps that lead from origin to destination -- it can find a path -- that eventually leads to a satisfaction of all of your terms. The problem with path-finding, is, of course, that it's a hard problem: there can be a combinatorial explosion, and thus an explosion of CPU time. There are algorithms that, for example, know all about 2D space, and make use of 2D geometry to find a good path. The backward chainer has no clue that it's exploring a 2D space, so it's search for a path is a bit more blind. Perhaps there's a way of making it clever, e.g. taking the A*-search rules and turning them into a PLN formula, and maybe that would work... but this discussion is not yet at this level. --linas -- cassette tapes - analog TV - film cameras - you -- You received this message because you are subscribed to the Google Groups "opencog" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/opencog/CAHrUA35gUeZhOLzDpYtDSrFXCAXSk8ueVEL5DRw2WRsRZuDxgQ%40mail.gmail.com.
