On Feb 13, 2008, at 2:14 PM, M. Scott Marshall wrote:
Dear Matt,
I see 'trust' as a 'view' that can be produced by running a filter
over
the data (provenance). The filter would implement my trust policy, or
one of them. In other words, my trust in a given 'agent' can be due to
the fact that it produces data using a certain algorithm. I also
place a
certain level of trust in the instrumentation that produced the data,
the p-values of an analysis in the processing pipeline, human
operators
involved, etc. So, the weights or confidence measures that you are
describing and that Alan is qualifying would be the *output* of such a
trust policy or filter. I would not besmirch the data with my own
personal trust models nor easily trust those of others. ;) I guess
that
what I'm trying to say is equivalent to Alan's point: I would
prefer to
keep facts and their evidence disclosed symbolically in the data so
that
different 'views' can take them into account.
But, before I go to build such 'views' or filters, I will wait for
that
sort of information to become machine-readable as data provenance. :)
However, I *can* try to make that sort of information available for
data
that I am helping to manage or produce. It seems that having a triple
store (such as Virtuoso) with named graph support would make it
possible
to produce several types of potentially useful data provenence.
The problem with NGs (and especially with existing RDF support) is
the close coupling between provenance and the URI from which the
triples were obtained.
If I wish to make available a collection of triples t1...tn where
each triple has its own provenance information tp1...tpn then I have
to have n URIs. If I serve up those triples through a SPARQL endpoint
then the act of creating a new graph will lose all the original NG
information.
NGs are not directly supported in the RDF model and it's not clear
how NGs would be accessed from an OWL-level API such as the OWLAPI.
There are proposed extensions such as Trix/Trig - and there may be
some relation between NGs and quoting in N3. However, AFAIK the
meaning of these extensions in the OWL-DL formalism is not clear.
I don't think NGs are so useful beyond SPARQL. I think the only
option here is to embrace rdf-reification (and to push for better
syntax, query and tool support). After all, this is how provenance at
the OWL level will work in OWL1.1 (i.e. annotating axioms)
-scott
--
M. Scott Marshall
http://staff.science.uva.nl/~marshall
http://adaptivedisclosure.org
Matt Williams wrote:
Dear Alan,
Thank you for making my point much more clearly than I managed. I'm a
little wary of probabilities in situations like the one you
describe, as
it always seems a little hard to pin down what is meant by them. At
least with the symbolic approach, you can give a short paragraph
saying
what you mean.
I'll try and find a paper on the "p-modals" (possible, probable,
etc.)
and ways of combining them tomorrow and put a paragraph on the wiki.
Matt
Alan Ruttenberg wrote:
I'm personally fond of the symbolic approach - I think it is more
direct and easier to explain what is meant. It's harder to align
people to a numerical system, I would think, and also provides a
false
sense of precision. Explanations are easier to understand as
well: "2
sources thought this probable, and 1 thought is doubtful" can be
grokked more easily than score: 70%
-Alan
On Feb 12, 2008, at 4:03 PM, Matt Williams wrote:
Just a quick note that the 'trust' we place in an agent /could/ be
described probabilistically, but could also be described logically.
I'm assuming that the probabilities that the trust annotations are
likely to subjective probabilities (as we're unlikely to have
enough
data to generate objective probabilities for the degree of trust).
If you ask people to annotate with probabilities, the next thing
you
might want to do is to define a set of common probabilities (10
- 90,
in 10% increments, for example).
The alternative is that one could annotate a source, or agent, with
our degree of belief, chosen from some dictionary of options
(probable, possible, doubtful, implausible, etc.).
Although there are some formal differences, the two approaches
end up
as something very similar. There is of course a great deal of
work on
managing conflicting annotations and levels of belief in the
literature.
Matt
--http://acl.icnet.uk/~mw
http://adhominem.blogsome.com/
+44 (0)7834 899570
