Re: Modal Concepts?

Hi Henry, all,

On 17/08/2021 11:03, Henry Story wrote:
> Hi,
>
>    I was wondering how many modal concepts could be deal with
> in N3. Perhaps there is already a good study of those?
>
> I guess we could perhaps say that Truth could be considered modal,
> and that is already defined with log:Truth.
>
> Necessity could be easy:
>
> { 2 + 2 = 4 } a log:Necessity .
>
> It means one could always add it to any graph, even those of one’s
> opponents. Perhaps definitions in ontologies are like that? Perhaps not.
>
> {cat color Green} log:Possible, may be a way of disproving something.

I guess we could define modalities as classes of quoted graphs, and add 
some axioms of the form


   { {?s ?p ?o} a :Necessity } => { ?s ?p ?o }.
   { ?s ?p ?o } => { { ?s ?p ?o } a :Possibility }.

   { ?f a :Necessity; log:includes { ?s ?p ?o }} => { {?s ?p ?o} a 
:Necessity }.
   { ?f a :Possibility; log:includes { ?s ?p ?o }} => { {?s ?p ?o} a 
:Possibility }.

but beyond that, what could we do with it? I am not an expert in modal 
logic, but my intuition is that without a proper negation, that won't 
bring us very far...

> Two that are particularly useful in computing are SHOULD and MUST,
> as they are used by ietf and w3c specs. It would be nice to at least
> be able to explain what kind of concepts those are. They somehow
> seem related to a goal Something MUST be done - if a goal (e.g. communication)
> is to be achieved.
It's an appealing notion, but could you develop it a little?
>
>
> Henry Story
>
> https://co-operating.systems
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>
>