Used to allow conditional content construction to be made streamable. Outputs the enclosed content only if the containing sequence generates no "ordinary" content.
Permitted parent elements: any XSLT element whose content model is sequence-constructor; any literal result element
Notes on the Saxon implementation
New in XSLT 3.0, and implemented since Saxon 9.7.
The following code generates a header and footer only if there is content,
however it is not guaranteed-streamable because it processes child
item-for-sale elements more than once:
To make this streamable, it can be rewritten using the