[Eulergui-user] Leverage on Drools to automatically retract GUI components

[Jean-Marc V. <jea...@gm...>]

Hi all


I experimented a way to leverage on Drools to automatically retract GUI
components and content when some domain fact triple is retracted from the
Knowledge Base. We leverage on Drools thruth maintenance (alias logicial
insert) .

How to test ( use
snapshot<http://eulergui.svn.sourceforge.net/viewvc/eulergui/trunk/eulergui/html/documentation.html#Install1>)
:


   1. Open test/n3JavaMapping-GUI.n3p<http://eulergui.svn.sourceforge.net/viewvc/eulergui/trunk/eulergui/test/n3JavaMapping-GUI.n3p>
   2. run Drools engine

   ==> a new Window with "data" appears
   3. Open N3 shell
   4. paste this in N3 shell:

   @prefix kb: <http://deductions.sf.net/ontology/knowledge_base.owl#>
. _:d kb:retract ( <http://test#x> <http://test#p> "data" ) .

   ==> in new Window , "data" disappears

How it works:

There is a Swing DefaultListModel associated to the URI :listModel .

Then the rule says: whenever there is a triple :x :p ?V , add ?V to the
ListModel .

:listModel a java:javax-swing-DefaultListModel.
{
  :x :p ?V .
} => {
  :listModel javam:addElement ( ?V ).
} .

The DefaultListModel is added in a JList object itself added to a JFrame (
standard Swing technology, just wrapped in N3 ) :

:JFRAME a java:javax-swing-JFrame .
:JLIST a java:javax-swing-JList .
:JLIST javam:setModel ( :listModel ) .

:JFRAME javam:add :JLIST .
:JFRAME javam:setSize ( 200 200 ) .
:JFRAME java:visible true .

So the scene is set at step 2.

As a by-product, this has added to the KB an object DeferredMethodCall that
represents the addElement() method call in the consequent of the rule. This
is N3 + Drools engine machinery ( BTW it allows to make calls deferred
until both subject and arguments are bound ) .

Now, when the triple :x :p "data" is retracted, Drools automatically
retracts the DeferredMethodCall object representing the addElement() method
call:

   - because the antecedent of the rule matches the retraction,
   - and because of thruth maintenance ( logicial insert ).

We added a class JavaObjectsRetractionListener implementing
WorkingMemoryEventListener which is called when the DeferredMethodCall
object is retracted. The listener calls removeElement when the method was
addElement (also another common pattern : remove and add methods names).

So the element "data" is removed from DefaultListModel, which removes the
list item in the window by standard Swing Model - View design pattern.


So, this amounts to "monitor" in real time in the GUI additions and
removals of N3 pattern:

:x :p ?V .

Of course the monitored pattern can be as complex as needed, or :x :p ?V. can
be a consequence by other rules.
-- 
Jean-Marc Vanel
Déductions SARL - Consulting, services, training,
Rule-based programming, Semantic Web
http://jmvanel.free.fr/ - EulerGUI, a turntable GUI for Semantic Web +
rules, XML, UML, eCore, Java bytecode
+33 (0)6 89 16 29 52
chat :  irc://irc.freenode.net#eulergui