Re: ldp:contains characteristics

On Mon, Apr 4, 2016 at 10:29 AM, Benjamin Armintor <armintor@gmail.com>
wrote:

>
> 1. There is a recommendation that HTTP PUT SHOULD NOT update containment
> triples (5.2.4), but no analogous recommendation for HTTP PATCH (5.2.7). Is
> this an intentional ambiguity, an oversight, or considered unnecessary as
> containment triples are server-managed?
>

Seems like an oversight to me. The intent (I believe) is that containment
triples SHOULD NOT be able to be modified by client's requests directly,
but reflect the results of creation and deletion events.


> 2. The recommendation on HTTP PUT for ldp:contains suggests that it is
> intended to be created only on resource creation, and thus be unique for
> the object of the containment triple - that is, ldp:contains might be
> (perhaps SHOULD be, following 5.2.4) understood as
> an owl:InverseFunctionalProperty. Is that a reasonable interpretation of
> the spec?
>

Hrm.  The answer to this is the answer to 3, as
owl:InverseFunctionalProperty has exactly the semantics described below,
no?

Basically -- is it ever possible to have two different contains ldp:contain
the same resource?  One way that might happen is if ldp:contains was used
as the object of ldp:hasMemberRelation and the membershipResource was set
to some random container. An Indirect container would make that even more
messy, as you could assert ldp:contains about random resources.  Nothing in
the spec (that I can see) forbids that...

So intent ... I was only part of the WG at the end, so certainly do not
claim any authority on the topic, but my understanding is that the intent
was that only one container should contain a resource.  Thus
InverseFunctional seems correct... if ?x ldp:contains ?y ; ?z ldp:contains
?y then ?x owl:sameAs ?z
And then any attempt to use ldp:contains in a ldp server like above should
result in an error.


Would love to hear other opinions.

Rob


3. I realize that this is contingent on the answers to the above as well as
> some implementation concerns, but how do people think this is affected by
> what OWL refers to as the "unique names" assumption (
> https://www.w3.org/TR/owl-ref/#IndividualIdentity)? Is the presence of
> more than one statement ?x ldp:contains <foo> a consistency problem, or an
> implication that all ?x are identifiers of the same resource?
>





>
>
> Thanks for your thoughts,
>
> Ben
>



-- 
Rob Sanderson
Information Standards Advocate
Digital Library Systems and Services
Stanford, CA 94305