I think Frank Meineke wrote:
>
> Hello,
>
> sorry, another newbie here - anyway, I have two questions:
>
> 1) (a easy one i hope)
> How do I retrieve a slot value from a fact?
>
> e.g.:
>
> ------------------------------------------------------
> (deftemplate aCar
> (slot color)
> )
>
> (deffunction printCar (?car)
> ; HERE IS THE PROBLEM
> ; fact-slot-value exists in CLIPS, but not in JESS (?)
> ; but it looks like a very basic functionality ?!
> ; (printout t "This car is: " (fact-slot-value ?car color) crlf)
> )
>
> (defrule listCars
> ?car <- (aCar (color red))
> =>
> (printCar car)
> )
Here's a version that will work with the upcoming Jess 4.2 (later this
week). To make it work with Jess 4.1, you'll have to edit
jess/Rete.java and make the findFactByID function public.
----------------------------------------------------------------------
import jess.*;
/**
* (C) 1998 Sandia National Laboratories and E.J. Friedman-Hill
*/
public class FactSlotValue implements Userfunction
{
public String name() { return "fact-slot-value"; }
public Value call(ValueVector vv, Context context) throws ReteException
{
Fact f = new Fact(context.engine().findFactByID(vv.get(1).factIDValue()),
context.engine());
return f.findValue(vv.get(2).stringValue());
}
}
----------------------------------------------------------------------
> ------------------------------------------------------
>
> 2) (a harder one)
> - As i understood JESS Objects / Templates do not support inheritance,
> such as
>
> (deftemplate aVehicle)
> (slot numberOfWheels)
> )
>
> What is the appropriate way now to mimick inheritance, such as
> (deftemplate aCar) ; is aVehicle
>
> (slot isAVehicle) ; this won't work, but I would have liked it
> (slot hasHorsePower)
> )
>
> (detemplate aBicycle) ; is aVehicle
> ...
> )
>
> - can slot values be templates again?
> - or should one use multislots preferably to templates
> - or should one use only ordered facts, where each level of inheritance
> adds new items?
>
None of the above. You should wait for Jess 5.0 (a first alpha version will
be released within a week), which support inheritance of deftemplates,
defclasses, deftemplates from defclasses, and defclasses from deftemplates.
>
> Thank you,
>
> Frank Meineke
>
> __________________________________________________________________________
> Dipl.Inform. Frank Meineke [EMAIL PROTECTED]
> Institut fuer Medizinische Informatik, Statistik und Epidemiologie (IMISE)
> Tel:+49-(0)341-9716111 Fax:9716109 URL:www.imise.uni-leipzig.de/~frank
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>
>
---------------------------------------------------------
Ernest Friedman-Hill
Distributed Systems Research Phone: (925) 294-2154
Sandia National Labs FAX: (925) 294-2234
Org. 8920, MS 9214 [EMAIL PROTECTED]
PO Box 969 http://herzberg.ca.sandia.gov
Livermore, CA 94550
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