Jess is certainly designed for this last mode of operation: you define
the "program" (the rules and queries), populate the data, and then run
the program. In general, you'll get the most efficient operation if
you do things that way.
Remember that pattern matching is done during working memory changes;
if you define your rules first, the load-facts itself is going to take
longer. On the other hand, rules are more efficient than queries
because issuing a query involves asserting a "probe fact" that
specifies the query parameters.
On Feb 16, 2009, at 7:45 AM, Ksawi wrote:
Dear all,
I figured out some interesting behavior of Jess when I was querying
it. I try to use Jess in forward chaining mode as a query machine. I
query Jess from Java (I use runQueryStar function).
For example: I have a file with 10540 facts and Jess script with
only 7 deftemplates. The script does not contain any rule or other
elements.
When I load facts (using load-facts function) and then I query the
Jess (query contains 20 patterns with about 25 tests, so it is the
big query I think :)) the querying time is 31719 ms.
But I think I found out better way to query the engine. I load facts
and then I add the same query as a rule to the engine (for example
(defrule name query =>)). Then I get activations (listActivations()
function) and all the tokens in activations are the answer for the
query. The querying time is 20969 ms.
But then I found out much better way: First, I add the query as a
rule and then I load all facts. Then I get activations and tokens
are the answer. The time is 12390ms.
In every case the number of results is the same (14892).
So I have a question – is that normal behavior or am I doing
something wrong? What is the reason of querying Jess even 3 times
faster?
Is there any way to calculate the computational complexity of
querying the Jess engine in forward chaining mode?
--
Best regards!
Jarek Bak
---------------------------------------------------------
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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