Outstanding! How about another twist, where a deftemplate inherits from a
defclass, e.g.
(defclass machine jess.examples.pumps.Machine)
(defclass pump extends machine jess.examples.pumps.Pump)
(deftemplate bigpump extends pump (slot foo))
I'm thinking about a non-Java programmer who is writing rules. They are
provided with a set of Java objects, but need to create a local subclass for
use within their rulebase.
-- Dave
At 02:28 PM 9/1/98 -0700, you wrote:
>Hi Folks,
>
>Just sharing a little bit of info about another Jess 4.2 feature:
>you'll be able to define inheritance relationships between
>deftemplates and between defclasses. Alan Davis was asking about this a
>little while ago, and I just had an insight yesterday about how
>to do this efficiently.
>
>Anyway, so what this looks like is this:
>
>(deftemplate t1 (slot A) (slot B) (slot C))
>(deftemplate t2 extends t1 (slot D) (slot E))
>(deftemplate t3 extends t1 (slot F) (slot G))
>
>Now you can write rules which match on patterns of type t1, t2, or
>t3. t2 has slots A,B,C,D,E, and t3 has A,B,C,F,G. Furthermore, rules
>written to match patterns of type t1 will also match t2 and t3; rules
>that match t2 or t3 patterns won't match the other, or t1.
>
>Similarly, with defclasses. I modified my 'pumps' example Beans such
>that both Tank and Pump inherit from a new class Machine, with one
>property (name). Then you can write
>
>(defclass machine jess.examples.pumps.Machine)
>(defclass pump extends machine jess.examples.pumps.Pump)
>(defclass tank extends machine jess.examples.pumps.Tank)
>
>and 'machine' rules will match either 'tank' or 'pump' patterns.
>
>Any comments on syntax, ideas for extensions, or subtleties, let me
>know. I considered using 'is-a' as COOL does instead of 'extends' -
>any opinions one way or the other?
>
>---------------------------------------------------------
>Ernest Friedman-Hill
>Distributed Systems Research Phone: (510) 294-2154
>Sandia National Labs FAX: (510) 294-2234
>Org. 8920, MS 9214 [EMAIL PROTECTED]
>PO Box 969 http://herzberg.ca.sandia.gov
>Livermore, CA 94550
>
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