[foaf-protocols] Person <-> Group (+sub/related groups) relations...

Dan Brickley danbri at danbri.org
Tue Nov 1 12:05:24 CET 2011

On 6 October 2011 09:07, Sebastian Tramp
<tramp at informatik.uni-leipzig.de> wrote:
> On Wed, Oct 05, 2011 at 09:55:37PM +0200, Henry Story wrote:
>> >> Can you elaborate on why you need a relationship named in this
>> >> direction? Rather than myGroup having a :member link to a person?
>> >
>> > In a distributed scenario, where both descriptions (the person WebID
>> > and the group WebID) are published by different authorities, we
>> > often choose to trust only in statements which have the subject =
>> > the linked data resource in our implementations. In the membership
>> > case here I would finally relate the group and the member only if
>> > both parties accept the relation (by publishing it). This can be
>> > much more complicated (e.g. refer to dgFoaf [1])
>> This sounds like an error. It is not the directions of the arrows that
>> matter with regard to trust, but who says what - and then how much we
>> trust them on the topic in question. So it is very important to keep
>> track of who is asserting the graphs.
> Indeed, and our policy is to trust only triple about the person as
> subject. This is a strong simplification but its very practical if your
> knowledge about the used vocabulary is very limited and if you have
> limited reasoning support in your application.

I hate to sound like Dr Spock here, but that just isn't logical...

Scenario 1:
Dan: "Let me in! this hotel is owned by me!"
Semweb-powered hotel door: "yeah right - piss off!"

Scenario 2:
Dan: "Let me in! I own this hotel!"
Semweb-powered hotel door: "Enter, gracious master! Would you like a
cup of tea?"

Perhaps "trust" is the wrong word for what's going on here. In RDF
there will eventually be lots of ways of saying the same thing. It is
perfectly fine for an RDF-consuming device or application to only
understand some of those patterns or idioms. But that isn't so much a
matter of trust, rather a question of what data patterns you



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