RE: [xsl] not() function behaving differently in java 1.4 and 1.5 environment.

["Michael Kay" <mike@xxxxxxxxxxxx>]

Looks like a bug. You are presumably using Xalan, so you should report it
there.

But it's likely to be a bug in the old version that's fixed in the new.
Can't be sure from your description.

> On a dry run we found the value of variable ($value) is null. 

There's no such thing as null in XPath.

One possibility is that $value is a result tree fragment containing a
document node with no children. This exhibits rather surprising behaviour
and products have been known to get it wrong. For such a value, not($value)
should give false(), $value='' should give true. This is consistent with the
1.5 results you are seeing.


>  The matrix below explains different test scenarios in which 
> we ran the test changing java version and replacing 
> not($value) with $value=''.
> 
> Java Version					Syntax Used
> Test Result	
> --------------------------------------------------------------
> ----------
> ------------------------------------------
>  1.4				<xsl:when test="not($value) and
> position() = 1">YES</xsl:when>		   True	
>  1.4				<xsl:when test="$value = '' and
> position() = 1">YES</xsl:when>	                      False	
>  1.5				<xsl:when test="not($value) and
> position() = 1">YES</xsl:when>	            False	
>  1.5				<xsl:when test="$value  = '' and
> position() = 1">YES</xsl:when>	            True	
> 
> The first test case is what the xsl originally looked like. 
> The same test fails in java 1.5 environment. Interestingly 
> changing the not() function with operator = (see test# 4), 
> the xsl works fine.
> 
> We have a couple of questions for this behavior:
> 
> *	Is there a difference in how a null and an empty string('') are
> interpreted in java 1.4 and java 1.5?

The XPath specification hasn't changed between java releases, if that's what
you mean. And there's no such thing as a null in XPath.


> *	Are the semantics of the statements we are using for not() and
> the = operator equivalent?

No. Given a node with a zero-length string value, boolean($node) returns
true and $node='' also returns true.

> *	Does XSL distinguish between null value and an empty string
> ('')?
> 

Not applicable, there's no such thing as null in XSLT/XPath.

Michael Kay
http://www.saxonica.com/