- From: Pat Hayes <phayes@ai.uwf.edu>
- Date: Tue, 11 Dec 2001 21:35:11 -0600
- 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 -- --------------------------------------------------------------------- IHMC (850)434 8903 home 40 South Alcaniz St. (850)202 4416 office Pensacola, FL 32501 (850)202 4440 fax phayes@ai.uwf.edu http://www.coginst.uwf.edu/~phayes
Received on Tuesday, 11 December 2001 22:35:23 UTC