Re: [xsl] My XPath mistakenly referenced an element that doesn't exist and I got no error message ... is this bad language design?

["dvint dvint@xxxxxxxxx" <xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx>]

For generic xml without a dtd or schema, there is no wrong XPath as who is to
say that element might exist somewhere or sometime. It would be nice if there
was a way to validate an XPath against a given did or schema to indicate a
path would never exist.Sent from my Verizon, Samsung Galaxy smartphone
-------- Original message --------From: "Roger L Costello costello@xxxxxxxxx"
<xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx> Date: 10/14/21  6:45 AM  (GMT-08:00)
To: xsl-list@xxxxxxxxxxxxxxxxxxxxxx Subject: [xsl] My XPath mistakenly
referenced an element that doesn't exist
 	and I got no error message ... is this bad language design? Hi Folks,Here is
my (very simple) XML document:	<Document>Hello, world</Document>My XSLT
program contains a xsl:value-of with a simple XPath expression:	<xsl:template
match="/">	B B B  <xsl:value-of select="Document/foo eq 'abc'"/>
</xsl:template>In the XPath expression I mistakenly referenced an element --
foo -- that does not exist.I ran the XSLT program on the XML document. No
error was generated.My colleague argues that such behavior is bad language
design:---------------------------------------------------Languages which
define such mistakes to just return "empty" node lists or false, or such are
not helping anybody. They just turn author mistakes into silent,
hard-to-detect behaviors.B  In my view this is a major mistake in the XPath
language. All path expressions should be strongly, statically type-correct, so
Document/foo has to be a possible path. But if element foo is optional, then
any given instance may not have element foo and so a path like Document/foo
can be type correct, but meaningless for a particular data document. One can
explicitly test, e.g., if ( exists(Document/foo) ) then (Document/foo eq
'abc') else.... If you just use the expression without this test, and node foo
doesn't exist, then it should cause a failure.
---------------------------------------------------Do you agree with my
colleague's assessment? Is this behavior in XPath an indication of bad
language design?/Roger