<HTML><BODY style="word-wrap: break-word; -khtml-nbsp-mode: space; -khtml-line-break: after-white-space; ">As I see it, this is not like SQL, because Tom said "<SPAN style=""><FONT class="Apple-style-span" color="#0000FF" face="Arial" size="2"><SPAN class="Apple-style-span" style="font-size: 10px;">null is returned when an access fails or some error occurs"<FONT class="Apple-style-span" color="#000000" face="Helvetica" size="3"><SPAN class="Apple-style-span" style="font-size: 12px;">, but then the guy</SPAN></FONT></SPAN></FONT></SPAN><DIV>who prepare the SQL statements has to be acknowloedge of the meaning of a null return, so he writes the querys in a</DIV><DIV>correct way to the application. Here thats not the case, the guy who writes the rules doesn't need to know why that</DIV><DIV>field is null, or 0 or blank, he ask for a statement of truth (field != 3), he spect not reason why that field is not 3, maybe </DIV><DIV>the value of the field is 0,1,2,4,5... null, " ", or whatever another value possible, he is just asking to not be specific one.</DIV><DIV>If someone need to manage the null value in a diferent way, then he must prepare the Fact Objects, Value Objects, Pojos,</DIV><DIV>Wrappers in a diferent way, design to do what he wants to be done with null values but not at the rules language level.</DIV><DIV><BR class="khtml-block-placeholder"></DIV><DIV>If I wanna ask for null value in a field to check for errors for example, I should ask for that " Fact( field == null )".</DIV><DIV><BR class="khtml-block-placeholder"></DIV><DIV>Maybe it could be a parametric flag somewhere telling the engine how to manage nulls, and set a default...</DIV><DIV><BR class="khtml-block-placeholder"></DIV><DIV>Another question: How the engine manage to return to Fact( field == null) when field is a primitive?, it makes autoboxing?,</DIV><DIV>comaparing Integer (for int) to null or something like that?, if the Engine do so, why?, maybe the rule's writer was wrong when</DIV><DIV>he wrote that, or maybe he just wanted to check if the field is blank/zero/not setter/etc... </DIV><DIV><BR class="khtml-block-placeholder"></DIV><DIV><BR class="khtml-block-placeholder"></DIV><DIV><DIV><DIV>On 15-03-2007, at 20:23, Michael Neale wrote:</DIV><BR class="Apple-interchange-newline"><BLOCKQUOTE type="cite">Felipe - yes that is consistent.<BR><BR>But what about:<BR><BR>Fact( field != 3 )<BR>now if field is null, its certainly not equal to 3, but should this be true? or because of null, it is always false? <BR><BR>In SQL, it would always be false. <BR><BR><DIV><SPAN class="gmail_quote">On 3/16/07, <B class="gmail_sendername">Felipe Piccolini</B> <<A href="mailto:felipe.piccolini@bluesoft.cl">felipe.piccolini@bluesoft.cl</A>> wrote:</SPAN><BLOCKQUOTE class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;"> <DIV style="">I think Im not agree with that... the question here is about how the Rule languaje will treat an expresion<DIV>made by a businness agent to the rules... so when a rule has a condition writen like this:</DIV> <DIV> Fact( field > 3)</DIV><DIV> this is asking : Is there a fact of type Fact which has a field and the value of that value is greater that 3..</DIV><DIV><BR></DIV><DIV>So, if the Fact actually exists and for 'some reason' its field "field" has a value which is not greater than 3 </DIV><DIV>(the rule doesn't need to know why the value is not 3, or is 0, or null or whatever) then the condition must</DIV><DIV>return (or been evaluated as) false. Its responsability for the DAO or fill implementation of the fact to put the </DIV><DIV>right value on its fields, the values that MEAN something. If its null it is possible that the value was never</DIV><DIV>setted or initialized, or maybe it means something else. If a bussiness guy wants to ask for been null </DIV><DIV> Fact( field == null) </DIV><DIV>then that question is a meaningfull one, dont let programmers decide what it means. If I wanna to ask for</DIV><DIV>being greater that 3, and it has no value, then the answer is NO, "it is NO greather than 3". </DIV><DIV><BR></DIV><DIV>well... this is just my humile opinion btw....</DIV><DIV><BR></DIV><DIV><BR></DIV><DIV><DIV><SPAN class="e" id="q_111570774ee63302_1"><BR><DIV><DIV>On 15-03-2007, at 13:03, Tom Gonzalez wrote:</DIV> <BR><BLOCKQUOTE type="cite"> <DIV><FONT color="#0000ff" face="Arial" size="2"><SPAN>We handle it as it can't be anything else but null cause null is returned when an access fails or some error occurs. This keeps it from falling into a valid evaluation and possibly a subtle bug going uncaught. </SPAN></FONT></DIV> <DIV><FONT color="#0000ff" face="Arial" size="2"><SPAN></SPAN></FONT> </DIV> <DIV><FONT color="#0000ff" face="Arial" size="2"><SPAN>Tom G</SPAN></FONT></DIV><BR> <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> [<A href="mailto:rules-dev-bounces@lists.jboss.org" target="_blank" onclick="return top.js.OpenExtLink(window,event,this)"> mailto:rules-dev-bounces@lists.jboss.org</A>] <B>On Behalf Of </B>Mark Proctor<BR><B>Sent:</B> Thursday, March 15, 2007 12:42 PM<BR><B>To:</B> Rules Dev List<BR><B>Subject:</B> Re: [rules-dev] need advice re null handling <BR></FONT><BR></DIV> <DIV></DIV>Its not about giving it up, its how we handle when those fields are null, do we treat it like a primitive and assume its 0, or do we say it can't be equal to anything else but null.<BR> <BR>In the following example neither y or z is defined, thus y is null and z is 0;<BR><BR>int x = 0;<BR>Integer y;<BR>in z;<BR>x == y // is false;<BR>x == z // is true<BR>y == null // is true<BR><BR>Mark<BR><BR>Tom Gonzalez wrote: <BLOCKQUOTE type="cite"> <DIV><SPAN><FONT color="#0000ff" face="Arial" size="2">The flexibility provided by an Object is very valuable. We use Integer and String objects all over the place today in our facts with drools. I would hate to give it up. </FONT></SPAN></DIV> <DIV><SPAN></SPAN> </DIV> <DIV><SPAN><FONT color="#0000ff" face="Arial" size="2">Tom G</FONT></SPAN></DIV><BR> <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> [<A href="mailto:rules-dev-bounces@lists.jboss.org" target="_blank" onclick="return top.js.OpenExtLink(window,event,this)"> mailto:rules-dev-bounces@lists.jboss.org</A>] <B>On Behalf Of </B>Mark Proctor<BR><B>Sent:</B> Thursday, March 15, 2007 6:29 AM<BR><B>To:</B> Rules Dev List<BR><B>Subject:</B> Re: [rules-dev] need advice re null handling <BR></FONT><BR></DIV>if bar is an integer it will be 0, if its an Integer it will be null. The Q is do we make Integer work like the primitive, or do we make it work like an Object.<BR><BR>Mark<BR>Michael Neale wrote: <BLOCKQUOTE type="cite"><A href="http://jira.jboss.com/jira/browse/JBRULES-627" target="_blank" onclick="return top.js.OpenExtLink(window,event,this)">http://jira.jboss.com/jira/browse/JBRULES-627</A><BR><BR>OK, this much is clear: <BR><BR>Foo(field == null) can be true if field is null.<BR><BR>but, what about Foo(field > 3), and field is null? should that be false? what about Foo(field != 3) - should that be true? <BR><BR>in SQL, null will always result in a false condition, unless you explicitly use null. <BR><BR>Thoughts? <BR><BR>Michael.<BR><PRE><HR size="4" width="90%">_______________________________________________<BR>rules-dev mailing list<BR><A href="mailto:rules-dev@lists.jboss.org" target="_blank" onclick="return top.js.OpenExtLink(window,event,this)">
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</PRE></BLOCKQUOTE><BR><DIV style="margin: 0px;">_______________________________________________</DIV><DIV style="margin: 0px;">rules-dev mailing list</DIV><DIV style="margin: 0px;"><A href="mailto:rules-dev@lists.jboss.org" target="_blank" onclick="return top.js.OpenExtLink(window,event,this)"> rules-dev@lists.jboss.org</A></DIV><DIV style="margin: 0px;"><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></DIV> </BLOCKQUOTE></DIV><BR></SPAN></DIV><DIV> <SPAN style="border-collapse: separate; border-spacing: 0px; color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px;"> <DIV><SPAN style="text-decoration: underline;"><SPAN> </SPAN></SPAN><DIV><FONT size="3"><SPAN style="font-size: 13px;"><B style="font-size: 13px; font-weight: bold;"> <SPAN style="font-size: 13px; font-weight: bold;">Felipe Piccolini M.</SPAN></B></SPAN></FONT></DIV><DIV><A href="mailto:felipe.piccolini@bluesoft.cl" target="_blank" onclick="return top.js.OpenExtLink(window,event,this)"> <SPAN style="color: rgb(0, 0, 238);">felipe.piccolini@bluesoft.cl</SPAN></A></DIV><BR></DIV><DIV><BR></DIV><BR></SPAN> </DIV><BR></DIV></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></BLOCKQUOTE></DIV><BR><DIV style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">_______________________________________________</DIV><DIV style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">rules-dev mailing list</DIV><DIV style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><A href="mailto:rules-dev@lists.jboss.org">rules-dev@lists.jboss.org</A></DIV><DIV style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><A href="https://lists.jboss.org/mailman/listinfo/rules-dev">https://lists.jboss.org/mailman/listinfo/rules-dev</A></DIV> </BLOCKQUOTE></DIV><BR><DIV> <SPAN class="Apple-style-span" style="border-collapse: separate; border-spacing: 0px 0px; color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; text-align: auto; -khtml-text-decorations-in-effect: none; text-indent: 0px; -apple-text-size-adjust: auto; text-transform: none; orphans: 2; white-space: normal; widows: 2; word-spacing: 0px; "><DIV><SPAN class="Apple-style-span" style="text-decoration: underline;; -khtml-text-decorations-in-effect: underline; "><SPAN class="Apple-style-span" style="-khtml-text-decorations-in-effect: underline; "> </SPAN></SPAN><DIV><FONT class="Apple-style-span" size="3"><SPAN class="Apple-style-span" style="font-size: 13px;"><B style="font-size: 13px; font-weight: bold; "><SPAN class="Apple-style-span" style="font-size: 13px; font-weight: bold; ">Felipe Piccolini M.</SPAN></B></SPAN></FONT></DIV><DIV><A href="mailto:felipe.piccolini@bluesoft.cl"><SPAN class="Apple-style-span" style="color: rgb(0, 0, 238); -khtml-text-decorations-in-effect: underline; ">felipe.piccolini@bluesoft.cl</SPAN></A></DIV><BR class="khtml-block-placeholder"></DIV><DIV><BR class="khtml-block-placeholder"></DIV><BR class="Apple-interchange-newline"></SPAN> </DIV><BR></DIV></BODY></HTML>