Re: JESS: How do I assert ordered facts from a map

Java classes are totally optional in Jess -- in fact, templates and  
facts created directly from the Jess language are always more efficient.

If Jess were to store the properties of an object in a Map -- so that  
they were dynamic and extensible at runtime -- then it would be  
considerably slower, for the same reason that fully dynamic languages  
in which objects are maps of code and variables are slower than  
compiled languages. Construction of a fast Rete network requires  
knowing what properties are being dealt with. Think of a database in  
which all the data was stored as object-attribute-value triples --  
would it be as fast as a database with fixed tables and columns?


On Aug 13, 2010, at 11:41 AM, Donald Winston wrote:

> So I have to create a template and know all the identifiers before  
> loading data into the fact base? This means I'll have to create java  
> bean objects for all my data. Every time the data changes I'll have  
> to modify the java classes. I don't believe in creating objects for  
> things that have little or no behavior. That's what Maps and Lists   
> are for.
>
> I suppose I could generate a "init-facts.clp" file when my app  
> starts up and load it along with the rules.
>
> On Aug 13, 2010, at 11:18 AM, Ernest Friedman-Hill wrote:
>
>> Basically for the same reason that you can't say something like  
>> this in Java:
>>
>> String theMethodName = "toString";
>> String myString = myObject.(theMethodName)();
>>
>> but instead you have to use reflection to find the method  
>> "toString" and call it using the Method object. The compiler needs  
>> to know the correct template to use to compile the code, and it  
>> can't do that if the name of the template is in a variable.
>>
>> Now, you may ask *could* it work the way you want? Indeed, it could  
>> -- but it doesn't at this time. We've talked in the past about  
>> allowing this kind of thing, and it has its pros and cons.
>>
>>
>> On Aug 13, 2010, at 11:05 AM, Donald Winston wrote:
>>
>>> Can anyone explain to me why this does not work? Why can't I use
>>>
>>> (deffacts initial-facts
>>> "Facts to trigger a few appropriate salient initialization rules."
>>> (assert-request-parameters))
>>>
>>> (defrule assert-request-parameters-rule
>>> "Assert stored data one time."
>>> (declare (salience 100))
>>> ?x <- (assert-request-parameters)
>>>       =>
>>> (foreach ?key (((fetch request-parameter-map) keySet) iterator)
>>>         (build str-cat "(assert (" ?key " " ((fetch request- 
>>> parameter-map) get ?key) "))"))
>>>          ; why not (assert (?key ((fetch request-parameter-map)  
>>> get ?key))))
>>>    (retract ?x))
>>>
>>> (bind ?map (new java.util.HashMap))
>>> (?map put one 1)
>>> (?map put two 2)
>>> (?map put three 3)
>>> (store request-parameter-map ?map)
>>> (reset)
>>> (facts)
>>> (run)
>>> (facts)
>>>
>>> Jess, the Rule Engine for the Java Platform
>>> Copyright (C) 2008 Sandia Corporation
>>> Jess Version 7.1p2 11/5/2008
>>>
>>> This copy of Jess will expire in 207 day(s).
>>> f-0   (MAIN::initial-fact)
>>> f-1   (MAIN::assert-request-parameters)
>>> For a total of 2 facts in module MAIN.
>>>
>>> f-0   (MAIN::initial-fact)
>>> For a total of 1 facts in module MAIN.
>>
>> ---------------------------------------------------------
>> Ernest Friedman-Hill
>> Informatics & Decision Sciences, Sandia National Laboratories
>> PO Box 969, MS 9012, Livermore, CA 94550
>> http://www.jessrules.com
>>
>>
>>
>>
>>
>>
>>
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>
>
>
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---------------------------------------------------------
Ernest Friedman-Hill
Informatics & Decision Sciences          Phone: (925) 294-2154
Sandia National Labs
PO Box 969, MS 9012                            [email protected]
Livermore, CA 94550                             http://www.jessrules.com





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