What is the difference between 'xsl:copy-of' and 'xsl:sequence'?

Question

What is the difference between 'xsl:copy-of' and 'xsl:sequence'

Answer 1

In very many situations they are interchangeable. One difference is that xsl:copy-of has more options (validation, copy-namespaces, etc). But most of the time you could use either.

There is a formal difference in that xsl:copy-of creates new nodes, while xsl:sequence returns a reference to existing nodes. That matters if, for example you use the "is" operator on the result, or if you use generate-id(), or if you navigate outside the subtree (e.g. to the parent of the copied node).

It's fair to say that 90% of the time people use xsl:copy-of in preference to xsl:sequence because that's what you did in XSLT 1.0, not because they really want a copy made.