[expertfinder-dev] Expertise and Trust Vocabs

[Tom Heath]

Hi Andreas, Hi all,

Just to check, did everyone who is on the ExpertFinder list receive my
mail about my Expertise (and other things) Vocabulary? If it somehow
got lost along the way then please let me know and do have a look at
the archive [1]. I've had some useful feedback already but would love
to have some more.

> Axel has mentioned that we should extend expressiveness of foaf:knows

Hmm, I'm not so sure. Creating another vocabulary to complement FOAF
by defining some additional and more expressive relations (that have
foaf:Person as domain and range) sounds fine, but lets not try and
overload FOAF with extra relationship semantics. We can (and should)
do this Web-style, by linking vocabularies.

> I think we should try to build that on top of the trust ontology [1], [2]
> from mindswap.

Hmm, now I'm positive that I disagree ;) ...

> I could imagine of building subproperties of different trust levels:
> foaf:knows might be a subproperty of trust:trust0
> foaf:loves could be a subporpety of trust:trust10

I think this would be really problematic. Firstly the modelling of
trust:trust[x] seems like a nasty hack for several reasons:

1) representation: can I really define my trust in someone as a 1-10
score? The literature on questionnaire design shows that above a
certain number people can't really distinguish between the options in
any meaningful way, so asking someone how much they agree with
something on a scale of e.g. 1-100 is totally futile. 1-7 is about the
limit for meaningful ratings. On the other hand, what about if I want
5.5, does that need another property in the ontology? Of course if
we're generating trust scores from some algorithm then scores are
unlikely to be integers, and we'll need to be able to represent that.

2) querying: imagine trying to do a SPARQL query to get all the people
from your FOAF file who you trust above average.... Imagine having to
search for all those properties in every query rather than just saying
trustValue > X.

Secondly, which I think is Asma's point, I think linking the semantics
of relationships with certain trust scores is not a sound way to
proceed, conceptually or technically. I may not love everyone I trust
10/10, or conversely I may not trust all my loved ones 10/10 (I love
my fictional brother, but wouldn't lend him a penny!). One just isn't
strongly predictive of the other.

Apologies if the response is overly strong; this is something that
comes up from time to time and I feel really strongly about it! :)

> and so on...
> first hand we won´t necessarily define all of the trust levels.
>
> the advantage of doing so is also that we can  use golbecks concept of
> TopicalTrust, which means:
>
> Agent A trusts Agent B concerning a special Topic/Concept/Skill etc.
>
> Which could be used in an application where users can rate the tags of other
> users and express
> "Okay, in that topic you´re an expert"
>
> And finally trust levels can be calculated automatically ;-)

I'm not sure if you've seen my draft Hoonoh ontology Andreas. It takes
a slightly different approach, but fulfils the same kind of role. For
example, using the ExpertiseRelationship class and associated
properties one can describe an expertise relationship between a
foaf:Person and a Topic (hoonoh:Topic, subclass of skos:Concept), and
assign this relationship a value. I hope that it's a relatively clean
bit of modelling, but would be pleased to get feedback.

What we're doing is generating metrics for these
ExpertiseRelationships (and ExperienceRelationships, and
ImpartialityRelationships) linking people to Topics, and two others
that link people to people (AffinityRelationship and
TrackRecordRelationship). By following this approach we can publish
one "opinion" (that generated by our algorithms) about someone's
expertise/experience/etc in a particular topic, but leave individual
applications to decide whether that person is trustworthy in a
particular context, and depending on the user needs (i.e. people's
thresholds for trustworthiness will defer).

> URIs for various skills & tags can be provided by dbpedia

Agreed. This is what we're planning, or at least topics that map to
dbpedia if possible.

<snip/>

> @tom, when do we start the website "Sparql query of the day"?

:D As soon as possible! Would contacting SWEO be a good strategy?
Uldis is a member of SWEO AFAIK and may be able to present the
proposal to that group. I imagine many of the members there would be
interested in the idea, and their contributions/backing would be very
helpful.

Cheers,

Tom.

[1] http://lists.foaf-project.org/pipermail/expertfinder-dev/2007-June/000209.html
[2] http://kmi.open.ac.uk/people/tom/tmp/draft-hoonoh-ontology.rdf
[3] http://kmi.open.ac.uk/people/tom/tmp/sample-hoonoh-instances.rdf