I just skimmed that code, and it does not seem to make use of the KR structures described in http://wiki.opencog.org/w/Claims_and_context and instead invents new link types .. e.g. BeliefLink. This leads to a proliferation: you'd need BeliefLink, SayLink, TellLink,UseToBeleiveInThePastLink, LieLink etc. So its not just a port, but a fairly serious restructuring.
--linas On Wed, Mar 15, 2017 at 11:14 AM, Ben Goertzel <[email protected]> wrote: > Code and theory for extending PLN to handle modal reasoning regarding > beliefs, knowledge and so forth is here: > > https://github.com/sumitsourabh/opencog/tree/ > patch-1/opencog/reasoning/pln/rules/epistemic-reasoning > > This was carefully worked out by Sumit Sourabh and Matt Ikle' a few years > ago. > > The code needs to be merged into the current version of PLN. This > would be a useful thing for someone to do, and then write associated > unit tests. > > -- Ben > > > On Wed, Mar 15, 2017 at 11:07 AM, Linas Vepstas <[email protected]> > wrote: > > > > > > On Sat, Mar 11, 2017 at 10:25 PM, Alex <[email protected]> > wrote: > >> > >> Hi! > >> > >> There can be modalities (which are usually expressed as diamonds or > boxes > >> (operators) in modal logic): > >> DUTY_TO_PERFORM_ACTION(agent, action, time horizone) - agent should > >> perform action within time horizon > >> BELIEF(agent, statement, time instant) - agent believes in statement at > >> the time instant > > > > > > > > Wasn't this discussed in some other thread, just recently? > > EvaluationLinks are the standard way of representing knowledge in > opencog. > > See wiki for that. > > > > Also see wiki about how to represent beleifs .. there is some section > there > > that discuses this, I don't recall where, or what it said. > > > > We've had prior discussions on the mailing list about representing > beleifs; > > but we only had a minimal discussion about reasoning over them. This is > one > > area that should be clearified, and if new PLN rules are needed to handle > > this, then now is a good time to figure that out. > > > > --linas > > > >> > >> > >> Such modalities are important in robotics (e.g. AGI safety - what duties > >> and permissions robots have) and in communication (modelling other agent > >> believes, knowledge and reasoning styles). > >> > >> Important point is, that by introducing modalities we also introduce > >> additional axioms/meta-rules that connect modal statements (statements > under > >> modal operator) with the nonmodal statements and with the statements of > >> other modalities (modal conversion). Example list of such metarules are > >> available in https://en.wikipedia.org/wiki/Modal_logic. Such metarules > >> sometimes are debatable, e.g. rule in deontic logic: > >> DUTY_TO_PERORM_ACTION(agent, action)->PERMISSION_TO_ > PERFORM_ACTION(agent, > >> action) and such metarules sometimes lead to paradoxes (classical > deontic > >> logic is full of them), nevertheless, such metarules expresses > additional > >> knowledge about reality. And such metarules can be mined and used for > >> constraining inference process (inference control)! > >> > >> I have two questions regarding expression of modalities in OpenCog?: > >> 1) how we can express modalities in Scheme/atomspace? > >> -- One solution is to introduce new link types. Is such introduction > >> possible? Maybe OpenCog have GenericLink for which the user form > derivation > >> and for the derivation the user can define syntax (how many Nodes and of > >> what Type are allowed in the new Link) and semantics (what processes are > >> done, what is output and strenght values of the output)? I have not > heard > >> about such option; > >> -- Another solution is to use PredicateNode, e.g. belief can be > expressed: > >> PredicateNode "agent_believe" > >> ConceptNode "Erving" > >> ConceptNode "Door is open" > >> The question is - can be use other Node, Link, result of > SatisfyingSetLink > >> etc. in place of the literal "agent_believes"? Or we are bounded for > using > >> literal constants in the PredicateNode? If former is true, then the > system > >> is open for the arbitrary set of modalities and the system can generate > new > >> modalities! > >> > >> 2) how we can express metarules for modalities in OpenCog?: > >> My proposal is to use rules that accepts some patterns of predicates and > >> that generates new predicates: > >> > >> rule_body(obligation_predicate_type_nodes)->rule_ > head(new_permission_predicate_type_nodes) > >> Again - the question is about flexibility of the system: is the system > >> allows generation of new link types or new predicate then the system can > >> mine/generate the relevant rules for the newly generate modalities! > >> > >> Of course, I am studying literature, experimenting, thinking about this, > >> but maybe someone also has thought about those questions and has already > >> something done - it would be nice to hear thoughts, proposals and > >> experience! > >> > >> Thanks! > >> > >> -- > >> 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 post to this group, send email to [email protected]. > >> Visit this group at https://groups.google.com/group/opencog. > >> To view this discussion on the web visit > >> https://groups.google.com/d/msgid/opencog/f70e8da1-1147- > 41e9-8aa6-c2acbab14ce6%40googlegroups.com. > >> For more options, visit https://groups.google.com/d/optout. > > > > > > -- > > 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 post to this group, send email to [email protected]. > > Visit this group at https://groups.google.com/group/opencog. > > To view this discussion on the web visit > > https://groups.google.com/d/msgid/opencog/CAHrUA36r01Q% > 3DKbXsJE3%2BS2KbpfQ3oZ5WD%2B-XY_dfPP6PCPhdEw%40mail.gmail.com. > > > > For more options, visit https://groups.google.com/d/optout. > > > > -- > Ben Goertzel, PhD > http://goertzel.org > > “Our first mothers and fathers … were endowed with intelligence; they > saw and instantly they could see far … they succeeded in knowing all > that there is in the world. When they looked, instantly they saw all > around them, and they contemplated in turn the arch of heaven and the > round face of the earth. … Great was their wisdom …. They were able to > know all.... > > But the Creator and the Maker did not hear this with pleasure. … ‘Are > they not by nature simple creatures of our making? Must they also be > gods? … What if they do not reproduce and multiply?’ > > Then the Heart of Heaven blew mist into their eyes, which clouded > their sight as when a mirror is breathed upon. Their eyes were covered > and they could see only what was close, only that was clear to them.” > > — Popol Vuh (holy book of the ancient Mayas) > > -- > 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 post to this group, send email to [email protected]. > Visit this group at https://groups.google.com/group/opencog. > To view this discussion on the web visit https://groups.google.com/d/ > msgid/opencog/CACYTDBdLatMo%2BSErmaU6g2An1YfiqmNcPBN_ru- > MNcFwxxY6Eg%40mail.gmail.com. > For more options, visit https://groups.google.com/d/optout. > -- 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 post to this group, send email to [email protected]. Visit this group at https://groups.google.com/group/opencog. To view this discussion on the web visit https://groups.google.com/d/msgid/opencog/CAHrUA34BEp9WsoTMMw44nT-%3DCv%2BQE1i9%3D2bRg-NvSmEsekzy1g%40mail.gmail.com. For more options, visit https://groups.google.com/d/optout.
