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RE: WebOnt Requirements - Summary

From: Pat Hayes <phayes@ai.uwf.edu>
Date: Tue, 11 Dec 2001 21:35:11 -0600
Message-Id: <p05101002b83c7d657e1e@[65.212.118.193]>
To: "Smith, Ned" <ned.smith@intel.com>
Cc: "'Jeff Heflin'" <heflin@cse.lehigh.edu>, herman.ter.horst@philips.com, dlm@ksl.stanford.edu, phayes@ai.uwf.edu, jos.deroo.jd@belgium.agfa.com, jjc@hplb.hpl.hp.com, "Smith, Ned" <ned.smith@intel.com>, Jim Hendler <hendler@cs.umd.edu>, www-archive@w3.org
>R3. Ontology evolution
>  > Ontologies can be changed over time and data sources can specify which
>>  version of the ontology they commit to.
>>  Issues:
>>  a) How does this differ from ontology extension (R2)? In R2, the
>>  original ontology is unchanged.
>Versioning features should (IMO) make it easy to apply revision control
>logic to scalar data. It seems reasonable to think of ontologies as scalar
>data in the sense that the version (number?) permeates all sub-elements.

?Why? Surely one might expect that changes would be incremental in 
large ontologies.

>  But
>the possible consequences of improperly managed versioning are profound.
>Consider a temperature sensor ontology that defines a temperature tolerance
>range between -10c and 100c. And an ontology change resulted in the sensor
>being clasified as a plasma temperature sensor then the tolerance range
>might mistakenly be interpreted as kelvin (in which case -10k to 100k is
>incompatible with device capabilities).

?? I don't see what this kind of example has to do with versioning. 
An ontology that could be broken this easily is just badly designed. 
For example it ought to refer to a standard ontology of temperature 
scales that would be maintained at some secure exterior URI, 
precisely to avoid this kind of problem arising.

>......>
>>  R9. Security
>>  Ability to specify who can view and modify information. Have
>>  ontologies
>>  that can specify access control information.
>>  Issues:
>>  a) Web typically doesn't allow update (except via file update) and
>>  viewing web pages is typically all or nothing, so how is this
>>  relevant?
>I interpret the semantic web to have peer-peer semantics. The browser based
>web (based on html/http) appears to be the origin of the "all or nothing"
>and "viewable" semantics. I'm not sure "viewable" and "web pages" are the
>right metaphores going forward?

Maybe not, but any changes need to be put in place at the FTP/HTTP 
layer, not in webont. The transfer protocols we have currently (and 
which are implicit in the meanings of URIs) do not provide for much 
subtlety in this area.

>The metaphore I've been using is that an
>ontology describes a structure that contains both data and meta-data,

I wish someone would say what that distinction amounts to. As far as 
I can see, DAML+OIL and RDFS consist of data.

>it is
>traversable and it can reveal new information at every traversal. It is
>reasonable to expect arbitrary sub-structures will be off-limits to some set
>of probers, for some set of operations, for some period of time.

How are the limits to be set? If I give you a URI, you can see what 
is there (or if it uses HTTPS, you can if you know the password.). 
There isn't any provision for controlling access on a more 
fine-grained basis.

>(If I'm
>misunderstanding ontology or misusing the metaphore someone please clarify -
>this is potentially a fundamental clarification).
>
>DAML-S supports the notion of a pre-condition which arguably is the right
>place to apply access control semantics. DAML-S is a services ontology which
>would be expressed using WOWG-ORL/WOL. I assume the DAML-S ontology would be
>public domain and readily accessible. However, proprietary extensions to a
>DAML-S ontology might redefine precondition, which implies introspection
>might also be limited. There is an element of circularity that is suspect. A
>ORL is used to describe an ontology that defines a semantic (precondition)
>that is needed to prevent unauthorized traversal of the ontology that
>originally defines the semantic.

I think that you are using 'precondition' in two different senses here (?).

>  > R13. Ontology querying
>>  Ability to ask questions about the logical structure of the
>>  ontology? Or
>>  is this something else?
>  > Issues:
>>  a) Are R12 and R13 the same requirement? May R12 is information
>>  retrieval and R13 is question answering?
>I would like to understand how an agent might know how not to get confused
>trying to learn the logical structure of say the network of post offices
>when the ontology describing the network may be full of indexed, replicated
>and distributed repositories whose physical structure (also represented by
>ontology) is mostly superfluous to what is wanted.

Is this more than just a classical inference search problem? If not, 
I think that the description logic reasoners can handle quite large 
data sets (10|4 to 10|5  assertions) without much trouble.

Pat
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Received on Tuesday, 11 December 2001 22:35:23 GMT

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