Re: possible stances with respect to multiple reification

On Mon, Apr 22, 2024 at 5:11 PM Franconi Enrico <franconi@inf.unibz.it>
wrote:

>
>
> On 22 Apr 2024, at 16:53, Jos De Roo <josderoo@gmail.com> wrote:
>
> On Mon, Apr 22, 2024 at 4:18 PM Lassila, Ora <ora@amazon.com> wrote:
>
>> Peter,
>>
>> this is good. I have some questions/observations, though:
>>
>> Option #1: On some level, we could say those examples are not RDF graphs,
>> but the question in my mind is about how easy/possible is it to detect
>> those cases? Detecting that "abc" :b :c is not an RDF graph is trivial, but
>> the reification case maybe not so much (at least there is a very different
>> implementation burden).
>>
>
> I gave it a try in eye and it is pretty straightforward to detect and
> throw an exception.
> For instance uncommenting line 9 or line 16 in
>
> https://github.com/eyereasoner/eye/blob/4c35d85322ecfe6c5a71e9e60a3cbfd964f7e9b3/reasoning/temp/edge.ttl
> throws a malformed_edge_extra_reifies/3 exception.
>
>
> Mmmhhh.
> Let’s first try to understand via some examples what is “illegality” of
> “multiple reification”.
>
> Is this graph illegal? I would say yes.
> << :r | :a :b 42 >> :c :d .
> << :r | :a :b 43 >> :c :d .
>
> Agreed


> Is this graph illegal? I would say no.
> << :r | :a :b _:x >> :c :d .
> << :r | :a :b _:y >> :c :d .
>
> Can live with that and implement tonight


> Is this graph illegal? I would say no.
> << :r | :a :b :e >> :c :d .
> << :r | :a :b :f >> :c :d .
>
> Is this graph illegal? I would say no.
> << :r | :g :h :e >> :c :d .
> << :r | :m :n :f >> :c :d .
>
> I see your point but have a hard time to implement that without
owl:differentFrom

Kind regards,
Jos


> —e.
>
> Option #3: Saying "can cause problems" is somewhat vague. Again, when do
>> you find out that there is a problem? What if we have an implementation
>> that simply refuses to ingest the "single reifier multiple triples" -style
>> graph? That would be a different kind of problem than the :range example
>> you give (ingestion vs. reasoning).
>>
>> I really would like to see how far we could take the idea of
>> "well-formedness". I understand it may not be easy to formalize, but I am
>> sure we could do better than what people say about pornography ("I cannot
>> define it but I know it when I see it"). Implementations could accept
>> non-well-formed graphs, or reject them. In case they do accept them,
>> outcomes could be unpredictable (ranging from practically nothing to
>> annoying or worse). People building systems that rely on predictable
>> behavior on non-well-formed graphs would be "on their own".
>>
>> Ora
>>
>>
>> On 4/22/24, 9:22 AM, "Peter F. Patel-Schneider" <pfpschneider@gmail.com
>> <mailto:pfpschneider@gmail.com>> wrote:
>>
>>
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>>
>>
>>
>>
>>
>>
>> I would find it useful to have an enumeration of the possible stances with
>> respect to multiple reification. I see four:
>>
>>
>> 1/ Multiple reification is completely illegal so
>> << :r | :a :b 42 >> :c :d .
>> << :r | :a :b 43 >> :c :d .
>> is not an RDF graph, just as
>> "abc" :b :c .
>> is not an RDF graph.
>>
>>
>> 2/ Multiple reification is possible but something to be avoided, like
>> :l rdf:first "abc" .
>> :l rdf:first "def" .
>> :l rdf:next rdf:nil .
>> is a valid RDF graph but is to be avoided or similar to
>> :age rdfs:range xsd:int .
>> :liz :age "abc" .
>> is a valid RDF graph but is to be avoided. That is, these graphs do not
>> make
>> sense for any purpose.
>>
>>
>> 3/ Multiple reification is possible but can cause problems and thus
>> should not
>> be encouraged, like
>> :r rdfs:subPropertyOf rdfs:subPropertyOf .
>> :r rdfs:subPropertyOf rdfs:subClassOf .
>> is a valid RDF graph but can cause problems or
>> :age rdfs:range xsd:int .
>> :liz :age :f .
>> is a valid RDF graph but can cause problems. That is, anyone who creates
>> these graphs should understand the consequences of what they are doing.
>>
>>
>> 4/ Multiple reification is possible and has no negative connotations, like
>> :liz :married :dick .
>> :liz :married :eddie .
>> is a valid RDF graph and has no problems as far as RDF is concerned.
>>
>>
>>
>>
>> I have a preferred stance here, a stance I cannot live with, one I can
>> live
>> with, and one I am uncertain about.
>>
>>
>> peter
>>
>>
> -- https://josd.github.io
>
>
>