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[protege-owl] Modeling change, source, uncertainty, contradiction?

Johann Petrak johann.petrak at chello.at
Wed Aug 22 06:11:58 PDT 2007


Matt Williams wrote:
> As a very simple approach to modelling time, you could use 
> time-interval-valid versions of the ontology. Not pretty, but might be 
> enough.
> 

For my purpose, I would be more interested in searchability than
deductability. In other words, I do not want to make deductions based
on time -- it would be sufficient to find properties of instances
 that are valid at a specific time. (So time would not be an issue
for classes, just for instances)
Naively I want an attribute "valid during" for each property/relation
between instances.
More generically I want several attributs: "valid during", "source"
etc.
The only thing I would need to do is to get the value of these
attributes out of the knowledge base and to search for triples
where these attributes match a specific pattern.

> DL ontologies will not handle conflicting information. To do that, you 
> need to use a defeasible formalism. There is a little bit of work on 
> ontologies & defeasibel reasoning.
> 
> I have used argumentation & ontologies; there's a paper at 
> http://acl.icnet.uk/~mw/WillliamsHunterICTAI07.pdf which also has 
> references to the other approaches.
Thank you for the reference. I am not sure I need it at such a
complex level though, since I do not need a reasoner to
come up with sets of entailed or conflicting facts.

I think it would be sufficient for me to be able to model
something like
  "source A indicates instanceX Rel1 instanceY"
  "source B indicates instanceX notRel1 instanceY"
or put differently
  instanceX Rel1-withattr: from source A instanceY
etc.

So it comes down to attatching searchable arbitrary attributes
to properties/relations again.

Could it be that I am missing something totally elementary
here because it seems that should be something that is needed
all the time?

Cheers,
  Johann
> 
> If you want to discuss this in more detail, email me off-list.
> 
> HTH,
> 
> Matt
> 
> Johann Petrak wrote:
>> I am pretty new to using Ontologies for knowledge represenation so
>> most of the tutorials and examples I have seen only are about
>> modeling some consistent set of unchanging facts.
>>
>> However, in real word situations it is often necessary to deal
>> with knowledge or information that has one of the following
>> complications:
>>
>> * a fact might change over time. More exactly, a property
>>   might be valid during some period of time but not another.
>>   Is it possible to model this in OWL ontologies and if yes,
>>   what are common design patterns to do it?
>>
>> * The fact that some instance has some property might be
>>   known based on sources A and B but might not be confirmed
>>   from source C. More problematic, it might contradict
>>   information from source D. So instead of some fact just
>>   "existing" we would like to model that it exists
>>   "according to source A" but "not confirmed by source C"
>>   and "not, according to source D"
>>   Is it possible to model this?
>>
>> * Sometimes it would be useful to attach a level of belief
>>   to a fact. E.g. some instance having some property might
>>   be likely but not certain.
>>
>> These things are probably differently hard to model, if at
>> all.
>> My biggest concern at the moment is change over time: for
>> most applications where I need some knowledge representation
>> it would be extremely important to be able to know that
>> e.g. some name was used during a certain time or that some
>> property existed during a certain period but not another.
>>
>> I would be thankful for any hints you could give me or
>> any papers or sources you could point out where these
>> issues are discussed.
>>
>> Johann
>>
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