<br> Michael,<br><br> No, it is good to "speak loud" about the problem so I can think more about it while doing it. :)<br> The problem is related to class inheritance. At compile time we know that a.b.c.Foo
is an event and we create an ClassObjectTypeConf for it, that says it is an event. At runtime, though, the user can insert instances (facts) of absolutely any class in the working memory... even classes for which there are no rules for. So, at runtime, when a fact of a class that was never seen before is inserted into working memory, we need to create a ClassObjectTypeConf for it, where we do a series of analysis (for instance, at this time we decide if a shadow proxy is needed for it or not), and at this time, we need to determine if this fact of a new "unknown" class (lets say
x.y.z.Bar) is an event or not (i.e, is it a subclass of a.b.c.Foo?). <br> So, back to my original e-mail, I can do that hierarchy analysis to transparently determine that, but it is a costly operation. The other alternative is assume that the user is explicit naming all event classes, but that will not work for automatically generated classes (like when using some XML binding frameworks). The last alternative is what your suggested of having a specific API for that, but wouldn't we need to create a checking algorithm anyway to prevent users mistakes?
<br><br> So, that is the dillemma... :)<br><br> []s<br> Edson<br><br><div><span class="gmail_quote">2007/11/9, Anstis, Michael (M.) <<a href="mailto:manstis1@ford.com">manstis1@ford.com</a>>:</span><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
<div>
<div dir="ltr" align="left"><span><font color="#0000ff" face="Arial" size="2">Hi Edson,</font></span></div>
<div dir="ltr" align="left"><span><font color="#0000ff" face="Arial" size="2"></font></span> </div>
<div dir="ltr" align="left"><span><font color="#0000ff" face="Arial" size="2">Sorry if I'm causing more pain and grief than you ever
intended your original posting to cause.</font></span></div>
<div dir="ltr" align="left"><span><font color="#0000ff" face="Arial" size="2"></font></span> </div>
<div dir="ltr" align="left"><span><font color="#0000ff" face="Arial" size="2">Now I understand (more) the use case for Events I can
better appreciate your original dilemma. If you need the information to optimise
the RETE network at compile-time why do you need to perform the check when a
Fact is inserted; couldn't you have a new ObjectTypeNode that is specific to
Event classes? If my lack of knowledge is more of a hindrance let me know and
I'll revert to being a passive observer.</font></span></div>
<div dir="ltr" align="left"><span><font color="#0000ff" face="Arial" size="2"></font></span> </div>
<div dir="ltr" align="left"><span><font color="#0000ff" face="Arial" size="2">Cheers,</font></span></div>
<div dir="ltr" align="left"><span><font color="#0000ff" face="Arial" size="2"></font></span> </div>
<div dir="ltr" align="left"><span><font color="#0000ff" face="Arial" size="2">Mike</font></span></div><font color="#0000ff" face="Arial" size="2"></font><font color="#0000ff" face="Arial" size="2"></font><br>
<blockquote style="margin-right: 0px;">
<div dir="ltr" align="left" lang="en-us">
<hr>
<font face="Tahoma" size="2"><span class="q"><b>From:</b> <a href="mailto:rules-dev-bounces@lists.jboss.org" target="_blank" onclick="return top.js.OpenExtLink(window,event,this)">rules-dev-bounces@lists.jboss.org</a>
[mailto:<a href="mailto:rules-dev-bounces@lists.jboss.org" target="_blank" onclick="return top.js.OpenExtLink(window,event,this)">rules-dev-bounces@lists.jboss.org</a>] <b>On Behalf Of </b>Edson
Tirelli<br></span><b>Sent:</b> 08 November 2007 15:50</font><div><span class="e" id="q_11623e379ad1f367_3"><font face="Tahoma" size="2"><br><b>To:</b> Rules Dev
List<br><b>Subject:</b> Re: [rules-dev] Determining if a class is an event or
not<br></font></span></div><br></div><div><span class="e" id="q_11623e379ad1f367_5">
<div></div><font color="#0000ff" face="Arial" size="2"></font><font color="#0000ff" face="Arial" size="2"></font><br> Michael,<br><br> The
engine *must* know, at rulebase compile time, what classes represent events.
When I say it is for optimization purposes, is because events are
"light-weight" facts with special characteristics, but that occur in huge
volumes, and so, the engine will never scale without knowing they are events.
The way we can make the engine aware that a given class is an event may vary:
<br><br>* we can use some "declaration statement" in the DRL like the ones I
described<br>* we can make the classes implement a markup-interface like
Matthias was suggesting<br>* we can use keywords, like iLog uses, writing
"event" in every pattern that represents an event <br><br>
Besides what I commented in a previous e-mail regarding the markup interfaces,
having the declaration statement in the DRL has an additional benefit of
making clear to third-parties reading the rules that those are event classes
(that carry special characteristics). <br><br> The idea here
is to discuss exactly the benefits and disadvantages of each approach.
:)<br><br> []s<br> Edson<br><br>
<div><span class="gmail_quote">2007/11/8, Anstis, Michael (M.) <<a href="mailto:manstis1@ford.com" target="_blank" onclick="return top.js.OpenExtLink(window,event,this)"> manstis1@ford.com</a>>:</span>
<blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
<div>
<div dir="ltr" align="left"><span><font color="#0000ff" face="Arial" size="2">I can
turn that question around...</font></span></div>
<div dir="ltr" align="left"><span><font color="#0000ff" face="Arial" size="2"></font></span> </div>
<div dir="ltr" align="left"><span><font color="#0000ff" face="Arial" size="2">If the
user has written objects MyFact and MyEvent is it fair to expect them to
have to declare it in the DRL?</font></span></div>
<div dir="ltr" align="left"><span><font color="#0000ff" face="Arial" size="2"></font></span> </div>
<div dir="ltr" align="left"><span><font color="#0000ff" face="Arial" size="2">I don't
know what Events are to do in Drools so don't which is the more reasonable
approach. Is it just for network optimisation as you say, or will Drools be
calling into members?</font></span></div>
<div dir="ltr" align="left"><span><font color="#0000ff" face="Arial" size="2"></font></span> </div>
<div dir="ltr" align="left"><span><font color="#0000ff" face="Arial" size="2">This is
much more interesting than (my) work ;-)</font></span></div><br>
<blockquote style="margin-right: 0px;">
<div dir="ltr" align="left" lang="en-us">
<hr>
<font face="Tahoma" size="2"><b>From:</b> <a href="mailto:rules-dev-bounces@lists.jboss.org" target="_blank" onclick="return top.js.OpenExtLink(window,event,this)">rules-dev-bounces@lists.jboss.org</a> [mailto:<a href="mailto:rules-dev-bounces@lists.jboss.org" target="_blank" onclick="return top.js.OpenExtLink(window,event,this)">
rules-dev-bounces@lists.jboss.org</a>] <b>On Behalf Of
</b>Edson Tirelli<br><b>Sent:</b> 08 November 2007 14:54<br><b>To:</b>
Rules Dev List</font>
<div><span><font face="Tahoma" size="2"><br><b>Subject:</b> Re: [rules-dev] Determining if a class is an
event or not<br></font></span></div><br></div>
<div><span>
<div></div><br> Michael,<br><br> Yes, the
session.insertEvent() API is something other engines (like iLog JRules)
have. I initially discarded that idea, but since you mentioned, we may
need to reconsider it.<br> Anyway, the API would solve this
part of the problem, but the whole scenario is: <br> The
engine must know at the compile time exactly what classes/interfaces used
in rules are events, so that it can optimize the network. That is
achievable by using any of the syntaxes bellow (I'm not sure which one to
use yet): <br><br>import event a.b.c.Foo; (or)<br>import event
a.b.c.*;<br><br>or explicit saying:<br><br>declare event
a.b.c.Foo;<br> <br> Once the user declared that
something is an event, do you think it is fair/acceptable to force the
user to use a different API to insert events into the engine?
<br><br>session.insert(); for regular facts<br>session.insertEvent(); for
events<br><br> []s<br> Edson<br><br>
<div><span class="gmail_quote">2007/11/8, Anstis, Michael (M.) <<a href="mailto:manstis1@ford.com" target="_blank" onclick="return top.js.OpenExtLink(window,event,this)">manstis1@ford.com
</a>>:</span>
<blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">Here's
my 2 cents - as a non-contributor to Drools codebase ;-)<br><br>You
could add insertEventFactTypeThingie to the API? Then you need just
<br>check that the class has been declared as an event in the DRL
similar to<br>what must already happen for normal DRL imports. I
personally don't have<br>issue with implementing a marker interface
(this is what frameworks like <br>Hibernate, EJB3 and Spring etc have
been imposing for years). What "wiring"<br>does the POJO need to become
an Event for use in Drools? Are you trying to<br>internalise too much at
the risk of making the event mechanism inflexible?
<br><br>Cheers,<br><br>Mike<br><br>-----Original Message-----<br>From:
<a href="mailto:rules-dev-bounces@lists.jboss.org" target="_blank" onclick="return top.js.OpenExtLink(window,event,this)">rules-dev-bounces@lists.jboss.org</a><br>[mailto:<a href="mailto:rules-dev-bounces@lists.jboss.org" target="_blank" onclick="return top.js.OpenExtLink(window,event,this)">
rules-dev-bounces@lists.jboss.org</a>] On Behalf Of Matthias<br>Sent: 08
November 2007 13:09<br>To: <a href="mailto:rules-dev@lists.jboss.org" target="_blank" onclick="return top.js.OpenExtLink(window,event,this)">rules-dev@lists.jboss.org</a><br>Subject: Re: [rules-dev]
Determining if a class is an event or not <br><br>Edson Tirelli
<tirelli <at> <a href="http://post.com" target="_blank" onclick="return top.js.OpenExtLink(window,event,this)">post.com</a>>
writes:<br><br>><br>><br>> All,
I reached a point where I need to make a design decision
and<br>would<br>like your opinion about it. Imagine the
following scenario: A user has a <br>domain model like
this:package a.b.c<br>> ;public interface Event { ... }package
x.y.z;public class MyEvent<br>implements<br>a.b.c.Event
{...} Then, in his DRL file he writes:package
p.q.r;import<br>event<br>a.b.c.* ; rule
Xwhen<br>> Event( ...
)then ...end So, it is clear that
a.b.c.Event should<br>be<br>handled as an event by the
engine. At runtime, the user asserts an object<br>of<br>the
class x.y.z.MyEvent into the working memory. Seems clear to me (and
<br>probably<br>to the user) that MyEvent should be handled as an event,
since by DRL<br>semantics,<br>> a.b.c.* are all events, and by OO
class hierarchy concept, since<br>a.b.c.Event<br>is an event,
x.y.z.MyEvent is an event too. My question is: how the
engine <br>knows that MyEvent is an event, since it only has the
x.y.z.MyEvent<br>> class as input? The only
answer I have is that when the first MyEvent<br>instance is asserted
into the working memory, we must get the class name and <br>iterate over
all event import declarations checking for a match. In case
no<br>one<br>is found, we need to repeat the process for each interface
and each class up<br>in<br>the MyEvent hierarchy. Once this process is
complete, we cache the results <br>in<br>the
ObjectTypeConf.<br>> This may be a quite heavy
process to be executed each time a fact of a<br>different class is
asserted in the working memory for the first time, but I<br>can't think
a different user-friendly way to solve the question.
<br>> The alternatives would be intrusive,
IMO, breaking the drools premise<br>to<br>work with user-defined POJOs
as facts: use anotations to annotate classes<br>that<br>are events, or
mandate users implement a specific interface for events.
<br>> Any better
idea? []s Edson --
Edson Tirelli Software<br>Engineer<br>- JBoss Rules Core
Developer Office: +55 11 3529-6000 Mobile: +55
11<br>9287-5646<br>> JBoss, a division of Red
Hat <at> <a href="http://www.jboss.com" target="_blank" onclick="return top.js.OpenExtLink(window,event,this)">www.jboss.com</a><br>><br>><br>>
_______________________________________________<br>> rules-dev
mailing list<br>> rules-dev <at> <a href="http://lists.jboss.org" target="_blank" onclick="return top.js.OpenExtLink(window,event,this)">lists.jboss.org </a><br>>
<a href="https://lists.jboss.org/mailman/listinfo/rules-dev" target="_blank" onclick="return top.js.OpenExtLink(window,event,this)">https://lists.jboss.org/mailman/listinfo/rules-dev</a><br>><br><br><br>Edson,
<br><br>I
got your striving not to mandate users implement a specific interface
for <br>events. However, why not at least introducing an empty event
interface (i.e.<br>a<br>marker interface, similar to the Serializable
interface in Java) the<br>user-defined event class(es) have to
implement? This way, when inserting a <br>MyEvent instance, you can
simply check whether it implements the event<br>interface<br>(by means
of 'instanceof'). Moreover, while parsing the import statements
of<br>a<br>rule file, it enables you to double-check whether all the
"event imports" <br>really<br>refer to classes implementing the (empty)
event interface.<br>In this regard, for me another question raises:
Without making any<br>restrictions<br>on the structure for a user
defined event class, how do you make sure it has
<br>all<br>the required attributes of an event (which in my
opinion must be a<br>timestamp,<br>at least) and how do you access them
(necessary for temporal relationships)?<br>Having said this, in my
opinion defining an empty event interface may not be <br>sufficient; in
addition, it must force the user to implement a
method<br>returning<br>the event's occurrence date (i.e. the timestamp)
at least... Or how would<br>you<br>handle this
issue?<br><br>Matthias<br><br>_______________________________________________
<br>rules-dev mailing list<br><a href="mailto:rules-dev@lists.jboss.org" target="_blank" onclick="return top.js.OpenExtLink(window,event,this)">rules-dev@lists.jboss.org</a><br><a href="https://lists.jboss.org/mailman/listinfo/rules-dev" target="_blank" onclick="return top.js.OpenExtLink(window,event,this)">
https://lists.jboss.org/mailman/listinfo/rules-dev</a>
<br><br>_______________________________________________<br>rules-dev
mailing list<br><a href="mailto:rules-dev@lists.jboss.org" target="_blank" onclick="return top.js.OpenExtLink(window,event,this)">rules-dev@lists.jboss.org</a><br><a href="https://lists.jboss.org/mailman/listinfo/rules-dev" target="_blank" onclick="return top.js.OpenExtLink(window,event,this)">
https://lists.jboss.org/mailman/listinfo/rules-dev</a><br><br><br></blockquote></div><br><br clear="all"><br>-- <br> Edson Tirelli<br> Software
Engineer - JBoss Rules Core Developer<br> Office: +55 11
3529-6000<br> Mobile: +55 11 9287-5646 <br> JBoss, a
division of Red Hat @ <a href="http://www.jboss.com" target="_blank" onclick="return top.js.OpenExtLink(window,event,this)">www.jboss.com</a>
</span></div></blockquote></div><br>_______________________________________________<br>rules-dev
mailing list<br><a href="mailto:rules-dev@lists.jboss.org" target="_blank" onclick="return top.js.OpenExtLink(window,event,this)">rules-dev@lists.jboss.org</a><br><a href="https://lists.jboss.org/mailman/listinfo/rules-dev" target="_blank" onclick="return top.js.OpenExtLink(window,event,this)">
https://lists.jboss.org/mailman/listinfo/rules-dev</a><br><br><br clear="all"></blockquote></div><br><br clear="all"><br>-- <br> Edson
Tirelli<br> Software Engineer - JBoss Rules Core
Developer<br> Office: +55 11 3529-6000 <br> Mobile: +55
11 9287-5646<br> JBoss, a division of Red Hat @ <a href="http://www.jboss.com" target="_blank" onclick="return top.js.OpenExtLink(window,event,this)">www.jboss.com</a> </span></div></blockquote></div>
<br>_______________________________________________<br>rules-dev mailing list<br><a onclick="return top.js.OpenExtLink(window,event,this)" href="mailto:rules-dev@lists.jboss.org">rules-dev@lists.jboss.org</a><br><a onclick="return top.js.OpenExtLink(window,event,this)" href="https://lists.jboss.org/mailman/listinfo/rules-dev" target="_blank">
https://lists.jboss.org/mailman/listinfo/rules-dev</a><br><br><br clear="all"></blockquote></div><br><br clear="all"><br>-- <br> Edson Tirelli<br> Software Engineer - JBoss Rules Core Developer<br> Office: +55 11 3529-6000
<br> Mobile: +55 11 9287-5646<br> JBoss, a division of Red Hat @ <a href="http://www.jboss.com">www.jboss.com</a>