Question

I am considering using either <xsl:param> or <xsl:variable> when defining an <xsl:template name="myTemplate"> that will be called in another XSL file.

Legacy code seems to use xsl:variable when being used in <xsl:template match="legacyTemplate">.

So what’s the difference between xsl:param and xsl:variable when using it in <xsl:template name="myTemplate">?

Answer 1

The difference is that the value of an xsl:param could be
set outside the context in which it is declared. For example,
see:

<xsl:template ...>
   <xsl:param name="p" select="'x'" />
   <xsl:variable name="v" select="'y'" />
...

then you know that $v will always give you the string 'y'. But for $p the string 'x' is only a default:
you will see a different value if the template is invoked with either
xsl:apply-templates or xsl:call-template which contains an instruction
such as:
<xsl:with-param name="p" select="'not x'" />

<xsl:param> may also be used outside xsl:template, at the top level in
the stylesheet. The value of such a parameter may be set when the
XSLT processor is called. How this is done depends on the processor
and whether you call it from the command line or by program.