Search Mailing List Archives

Limit search to: Subject & Body Subject Author
Sort by: Reverse Sort
Limit to: All This Week Last Week This Month Last Month
Select Date Range     through    

[protege-owl] how can I model NULL data values in OWL?

Timothy Redmond tredmond at
Wed Feb 22 09:36:19 PST 2012

On 02/22/2012 05:53 AM, Dennis Pierson wrote:
> Hi,
> I have instances with unpopulated values. Specifically I want to model 
> NULL dates. I can't find any mention of null or unpopulated datatypes 
> in the OWL or XSD documentation. Is there any way to do this? Pellet 
> won't accept it ("");

The real question here is what do you mean by this "NULL" value.  OWL 
lets you pick the semantics that you want (there are at least three 
possibilities).  I give an example of these these three cases in the 
attached ontology.

First, you could be creating an individual that you know cannot have a 
dateTime.  I have created an instance like this with the following axioms:

    Individual: knownNotToHaveADate
             not (dateProperty some rdfs:Literal),

This asserts that the individual knownNotToHaveADate cannot have any 
dateProperty property value.

Second, you could be asserting that a particular individual has a 
property value but you just don't know what it is.  I have created an 
instance like this with the following axioms:

    Individual: hasUnknownDate

             dateProperty some xsd:dateTime,

Here the individual hasUnknownDate has some dateProperty and this value 
is a dateTime but it is not known what value this property has.

Finally, you could have an individual where you don't know if or what 
dateProperty value it has.  In this case you don't have to say anything 
- OWL does not assume anything one way or the other.

I also made some test classes so that you can run a reasoner and see 
that the individuals classify into the right classes.  In particular the 
couldHaveADate individual is not found to be in either the MustHavaDate 
or the DatedButNoDate classes.


> Thank you
> Dennis
> ------------------------------------------------------------------------
> Information transmitted by this e-mail is proprietary to MphasiS, its 
> associated companies and/ or its customers and is intended for use 
> only by the individual or entity to which it is addressed, and may 
> contain information that is privileged, confidential or exempt from 
> disclosure under applicable law. If you are not the intended recipient 
> or it appears that this mail has been forwarded to you without proper 
> authority, you are notified that any use or dissemination of this 
> information in any manner is strictly prohibited. In such cases, 
> please notify us immediately at mailmaster at and delete this 
> mail from your records.
> _______________________________________________
> protege-owl mailing list
> protege-owl at
> Instructions for unsubscribing:

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: NullValue.owl
Type: application/rdf+xml
Size: 5725 bytes
Desc: not available
URL: <>

More information about the protege-owl mailing list