[Jboss-svn-commits] JBL Code SVN: r4033 - labs/jbossrules/trunk/documentation/manual/en/Chapter-Rule_Engine

[<jbo...@li...>]

Author: mic...@jb...
Date: 2006-05-02 03:34:20 -0400 (Tue, 02 May 2006)
New Revision: 4033

Modified:
   labs/jbossrules/trunk/documentation/manual/en/Chapter-Rule_Engine/Section-Agenda.xml
Log:
more goodness

Modified: labs/jbossrules/trunk/documentation/manual/en/Chapter-Rule_Engine/Section-Agenda.xml
===================================================================
--- labs/jbossrules/trunk/documentation/manual/en/Chapter-Rule_Engine/Section-Agenda.xml	2006-05-02 06:13:36 UTC (rev 4032)
+++ labs/jbossrules/trunk/documentation/manual/en/Chapter-Rule_Engine/Section-Agenda.xml	2006-05-02 07:34:20 UTC (rev 4033)
@@ -2,24 +2,71 @@
 <section>
   <title>Agenda</title>
 
-  <para>The agenda is a RETE feature. It is an area where rules + matching
-  facts are kept before they are fired.</para>
+  <para>The agenda is a RETE feature. It is an area in memory where rules +
+  matching facts are kept before they are fired.</para>
 
+  <para>The engine operates in a "2 phase" mode: 1) working memory actions
+  (this is where most of the work takes place) and 2) agenda evaluation (where
+  rule actions are fired). It is important to note that this process is
+  recursive, in that a rule firing may cause working memory actions to occur.
+  When working memory actions are taking place, no rules are being fired.
+  </para>
+
+  <para>The items that are placed on the agenda are called "activations" which
+  are a rule plus matched facts (facts that at that point in time allow the
+  rule to fire).</para>
+
+  <para>The fileAllRules() method causes the agenda to be evaluated, and
+  eventually the activations "fired". The process recurses until the agenda is
+  clear, in which case control returns to the calling application.</para>
+
+  <para>Working memory actions are assertion of new, modification of exsiting
+  and retraction of facts.These are all triggered from the RHS of a rule, or
+  in java code.</para>
+
   <section>
     <title>Conflict Resultion</title>
 
-    <para></para>
+    <para>Conflict resolution is required when there are mutliple rules on the
+    agenda. As firing a rule may have side effects on working memory, the rule
+    engine needs to know in what order the rules should fire (for instance,
+    firing ruleA may cause ruleB to be removed from the agenda).</para>
+
+    <para>Drools employes a variety of strategies here. The most visible one
+    is "salience" or priority, in which case a user can specify that a certain
+    rule has a higher priority (by giving it a higher number) then other
+    rules. In that case, the higher salience rule will always be
+    preferred.</para>
+
+    <para>As a general rule, it is a good idea not to count on the rules
+    firing in any particular order, and try and author the rules without
+    worrying about a "flow". </para>
+
+    <para>The conflict resolution strategies emplyed by drools are: Salience,
+    FIFO (first in, first out), Total Recency and Load order.</para>
+
+    <para>If salience does not provide a resolution, the FIFO is used (items
+    that are in the agenda longer are preferred). Failing that totally recency
+    of the activation (how new the facts are) is used before reverting to the
+    arbitrary load order (which is nominally the order in which the rules were
+    declared).</para>
   </section>
 
   <section>
     <title>Agenda Groups</title>
 
-    <para></para>
+    <para>Agenda groups are a way to partition rules (activations, actually)
+    on the agenda. At any one time, only one group has "focus" which means
+    that the activations for rules in that group will only take effect (you
+    can also have rules "auto focus" which means the focus for its agenda
+    group it taken when that rules conditions are true).</para>
   </section>
 
   <section>
     <title>Filters</title>
 
-    <para></para>
+    <para>Filters are optional implementations of a the filter interface which
+    are used to allow/or deny an activation from firing (what you filter on,
+    is entirely up to the implementation).</para>
   </section>
 </section>
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