Appendix F: Backwards Compatibility

Overview

This appendix summarizes the areas where XSLT 2.0 is not fully backwards compatible with XSLT 1.0. You can think of the transition from XSLT 1.0 to XSLT 2.0 as happening in three stages, though you may choose to do all three at once:

• The first stage takes the stylesheet unchanged, still specifying «version= "1.0" » , and runs it under an XSLT 2.0 processor instead of an XSLT 1.0 processor.

• The next stage is to change the stylesheet to specify «version=" 2.0" » . This has the effect of switching off backwards compatibility mode.

• The final stage is to modify the stylesheet to take advantage of new facilities introduced in XSLT 2.0 and XPath 2.0: most notably, the ability to validate the source documents against a schema.

There is potential for transition problems to occur at each of these three stages. The focus in this appendix, however, is on the first two stages, because once you start changing your stylesheet or your application, it's very much under your own control whether existing code keeps working.

In this appendix we'll treat the XSLT changes and the XPath changes together.