Saxon

This certainly shouldn't work and a quick test shows that it doesn't: I get

Saxon-EE 9.7.0.21J from Saxonica
Java version 1.8.0_121
Using license serial number V008779
URIResolver.resolve href="{$globalParameterName}" base="file:/Users/mike/Desktop/temp/test.xsl"
Error on line 5 column 47 of test.xsl:
  Invalid relative URI {{$globalParameterName}}: Illegal character in path at index 0:
  {$globalParameterName}
Invalid relative URI {{$globalParameterName}}

So there's something going on here behind the scenes that we don't know about...

What should work here in 3.0 is a static parameter:

<xsl:param name="globalParameterName" static="yes" as="xs:string"/>
...
...
<xsl:include _href="{$globalParameterName}"/>

Hi Michael. Thanks for the quick follow-up and confirmation.

There's a minor difference in version number. We're on version 9.7.0.12 and I see your test was on .21. Not sure if maybe this is an issue in .12 that was fixed in .21?

I did have a solution that was based on static parameters, but due to considerations in my environment/platform outside of Saxon, that had some implications that I wanted to avoid. ...which is what led me to trying the above.

The upshot here for me is the confirmation that this behavior (however it's manifesting) is not expected behavior and not something I should code to. If this isn't a confirmed bug for 9.7.0.12, I'll let you know if I come across an explanation for what I'm seeing just to close the loop.

It seems very unlikely that this was a bug fixed between 9.7.0.12 and 9.7.0.21. There was over a year between these releases, so a lot could have happened, and it's a long time ago (2017) so I wouldn't necessarily remember; it just doesn't seem a very likely bug. I'm not going to install the .12 release from archive just to find out - sorry!

I would mention also that 9.7 was released before the XSLT 3.0 specification was completely finished, and although they're likely to be minor, there may be changes in subsequent versions that bring the product into line with the spec. The current release is 10.1.

Understood, and agree it's not worth the effort of backing up to .12 to confirm. I have what I need to know to make the necessary decision in this particular solution.

That's good information re: 9/7 vs. the spec completion. Thank you!