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Re: more text / Trust bipolar decision or continuum

From: Pat Hayes <phayes@ihmc.us>
Date: Wed, 17 Mar 2004 12:49:13 -0600
Message-Id: <p06001f16bc7e4ae1943d@[10.0.100.76]>
To: "Chris Bizer" <chris@bizer.de>
Cc: "Patrick Stickler" <patrick.stickler@nokia.com>, "Jeremy Carroll" <jjc@hpl.hp.com>, <www-archive@w3.org>

>We tend to see trust as a bipolar decision by an agent. You trust a graph or
>you don't trust it. This conflicts with the view of the majority of trust
>researchers, who see trust as a continuum.
>
>See quote from one of my documents below:
>"There is a wide range of different trust definitions known from physiology,
>sociology, economic science and computer science. There is no general
>agreement on the term "Trust". A comparison of the different views on the
>topic and the different trust definitions can be found in [Marsh94] and
>[Gambetta00]. Following Joseph M. Reagle [Reagle02], we define trust as:
>Trust (worthiness) is the degree to which an agent (human or machine)
>considers information to be true for a given time and context.

Is trust then always and only concerned with truth of information? 
That seems rather restrictive as a general theory. For example, there 
are people I know who I trust to be rational, or to be objective, or 
to be honest: but none of this means that I necessarily believe what 
they say to be true.

>Our definition refers to the following aspects of trust:
>-There is uncertainty in trust situations, which cannot be eliminated. It is
>only possible to minimize uncertainty.

One can make similar claims about any situation involving 
propositional attitudes of any kind. Such philosophical havering is 
easy, but not convincing unless it is backed up by some deeper 
analysis. (IMO). Is there anything special about trust that makes it 
inherently continuous? If anything, the potential link to action and 
agency usually makes things more polar, not less polar, since its 
impossible to act in a continuum: you either do the action, or not.

>-Trust is subjective. Different users have different views of the world and
>different subjective trust requirements in the same situation.
>-Trust depends on the context and changes over time.
>-Trust in a continuum and no bivariate property.

None of this seems convincing to me. It reads like pop sociology.

>"
>
>This conflicts with what we write in  Chapter 4:
>
>"The meaning of a set of named graphs depends on a separate decision about
>which of the graphs to accept. We represent this decision as a set A of
>nodes naming the accepted graphs. The meaning of a set of accepted named
>graphs hA,Ni is given by taking the graph merge Sa2A N(a), and then
>interpreting that graph using the semantics of RDF[?]. Any extension
>semantics of RDF can be used; in this paper we uniformly use those of OWL
>Full[4]."
>
>I totally agree with Jeremy, that for practical reasons we should have a
>bipolar view on trust in the context of the Semantic Web at it's current
>state of development. But the interesting question is: Is this bipolar view
>required for RDF semantics or OWL to work or can we be open to agents using
>continuum based trust models (modal logic ??) ?

OWL and RDF are inherently bipolar (boolean 2-valued) in their basic 
assertional semantics. However, one can make assertions about a 
continuum within a boolean language, provided that you refer to the 
values somehow (which would likely be a good idea anyway). You can 
say that (it is true that) my trust in foo is 0.1637, or that my 
trust in foo is greater than my trust in baz. You can have a 
multivariate-valued trust datatype if you want :-)

So I don't think we are *excluding* anything by having a 
truth-functional language to say it all in. The logic is one thing, 
the content another. Messing with the logic is usually not as 
practical as inventing an ontology of your own favorite continuum.

Pat

>
>I don't mandate, that we should include this stuff in the paper, but it
>would be nice if our approach wouldn't exclude future agents that might use
>continuum based trust models (and will have the unlimited processing power
>to reason based on these models :-). In addition it would make our work less
>attackable for the trust community.
>
>Chris


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Received on Wednesday, 17 March 2004 14:00:50 UTC

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