Serna supports the subset of XInclude V1.0 W3C Recommendation 20 December 2004.
The supported (and meaningful to Serna) xi:include attributes are href, xpointer, encoding, parse.
The fallback with xi:fallback is supported. Note, however, that the content of xi:fallback element is not directly editable. Insert the content of the element in the text mode.
For href only URLs are supported. For xpointer the XPointer shorthands are supported (ability to include by element ID), as described in Section "Shorthand Pointer" of the XPointer Framework W3C Recommendation 25 March 2003.
If parse="text" and the encoding is not explicitly specified with the XInclude Attributes, then the encoding of the included document is considered to be the current document encoding.
Schema validation is applied with the same schema as used by the xincluding document when xincluded document is inserted into the xincluding document.
The IDs of the xincluded document are resolved as if included document is the part of the root document. I.e. the errors are reported if the IDs are clashed or missing.