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[protege-discussion] slots

Jonathan Carter jonathan.carter at
Wed Nov 12 12:49:43 PST 2008

Hi Jason,

No, there's no date / time slot. I normally use a String for this.  
Might be worth checking the Protege add-ons / widgets to see if  
someone's made a date / time slot widget that validates that the  
entered string is a proper date/time.

For the units, again, as far as I am aware, there's nothing that does  
what you describe. However, it's important to note that semantics are  
very important for slots and it's better to be as specific as  
possible. So, I would recommend have a float-value slot that is  
defined to be for one unit type - e.g. length_in_mm - only and if you  
need to optionally capture the length in inches, have a  
length_in_inches slot. That way, anything/anyone interrogating the  
ontology will know what units the value is by the slot that's used,  
not from any string characters in the slot value. After all, 3 inches  
is not the same as 3mm!
My recent experience is that it is best to have multiple slots that  
have specific semantics rather than fewer slots that can have multiple  
interpretations (which leads to confusion). I've had to refactor my  
class structure to resolve this recently.
I realise that this might seem a bit odd compared to normal  
engineering practise but the ontology is all about precise semantics  
and it makes the Protege forms clearer to use.

Hope this helps

Jonathan Carter - Head of Technical Architecture
Enterprise Architecture Solutions Ltd
Mobile: +44 (0) 7904 198295
Email: jonathan.carter at

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On 12 Nov 2008, at 20:39, Jason Sachs wrote:

> is there a way to restrict a slot of type String to a date/time  
> value? (I don't see a Date or Time type)
> also is there any way to associate engineering units with a Float  
> value? (like if I want a length in millimeters) I don't really need  
> a user to change units, but it is disconcerting in the Instance  
> Editor if they will type in a floating-point value without any  
> indication of whether it's supposed to be mm or inches or feet or  
> whatever.
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> protege-discussion mailing list
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