Thanks for the dog analogy...
But going back to practical uses, one aspect that I like when creating a
fact directly from a from-class template (i.e., a doghouse without a dog --
I can still make some reasoning over the doghouse) is that the Jess code to
do it is much more readable and compact, since you provide values for named
slots.
Something like:
(deftemplate Person (declare (from-class Person)))****
(assert (Person (name "Henrique") (age 38)))
When using definstance, I would have to go:
(bind ?p (new Person "Henrique" 38)) ; assuming there is such a
constructor
(definstance Person ?p)
or
(bind ?p (new Person))
(?p setName "Henrique")
(?p setAge 38)
(definstance Person ?p)
Now, when you have a class with many data members this becomes quite
complex.
Any comments? Thanks!
Henrique
On Fri, May 10, 2013 at 3:21 PM, Friedman-Hill, Ernest
<ejfr...@sandia.gov>wrote:
> The **real** way to add shadow facts is using the “definstance”
> function. It has a number of options that aren’t available with “add”. The
> “add” function was added to Jess to support the simplified semantics of
> JSR-94 (the javax.rules API) but the intent is that most Jess users will
> use “definstance.”****
>
> ** **
>
> Asserting a fact directly from a from-class template is like buying a
> doghouse; you don’t expect to go out the next morning and find that somehow
> it has a dog in it, right? It’s certainly something you can do, but in
> normal life it’s not very useful; usually you get a doghouse when you buy a
> dog, and “add” and “definstance” will both get you a doghouse for your Java
> object “dog” automatically.****
>
> ** **
>
> *From:* owner-jess-us...@sandia.gov [mailto:owner-jess-us...@sandia.gov] *On
> Behalf Of *Henrique Lopes Cardoso
> *Sent:* Friday, May 10, 2013 4:54 AM
> *To:* jess-users
> *Subject:* JESS: [EXTERNAL] Adding facts that are instances of from-class
> deftemplates****
>
> ** **
>
> Hi,****
>
> ** **
>
> I am concerned with the at least two different ways in which you can add,
> to working memory, facts that are instances of from-class deftemplates.***
> *
>
> Lets say I have:****
>
> ** **
>
> (deftemplate FC (declare (from-class FC)))****
>
> ** **
>
> I can add a shadow fact like this:****
>
> ** **
>
> (bind ?fc (new FC))****
>
> (add ?fc)****
>
> ** **
>
> This is the general approach described in Section 5.3.2 of the Jess manual.
> ****
>
> But I can also simply go like:****
>
> ** **
>
> (assert (FC))****
>
> ** **
>
> I guess in this case I do not get a shadow fact, since the OBJECT slot is
> nil.****
>
> ** **
>
> So, my question is: if my facts are not supposed to be changed from Java
> code, is there any difference in using each of these approaches?****
>
> Section 5.3 from the Jess manual does not even mention that instances of
> from-class deftemplates can be created using the second approach above.***
> *
>
> ** **
>
> Thanks!****
>
> ** **
>
> Henrique****
>
> ** **
>
--
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Henrique Lopes Cardoso
DEI/FEUP
Rua Dr. Roberto Frias | 4200-465 Porto
PORTUGAL
VoIP: (+351) 220413355
Phone: (+351) 225081400 ext.1315...@fe.up.pt | www.fe.up.pt/~hlc
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