I see "type aliases" in the XPath 4.0 Spec, though I don't remember us ever voting to include this.

And in section  "2.2.1 Static Context" there is this text:

"*Note:*

Item type aliases can be defined in XQuery 4.0 and in XSLT 4.0, but not in
XPath 4.0 itself."

I clearly remember that we had a heated and unfinished argument whether or
not defining type aliases can be done in XPath and that we didn't arrive at
conclusion, so we accepted that we will see a demonstration how type
aliases can be defined once in XPath and accessed and reused from multiple
XPath expressions.

Here is an action from one of the minutes (apr. 11):

     * [ ] QT4CG-029-07: NW to open the next discussion of #397 with a
       demo from DN

And the issue for type aliases is with Open status.

I don't remember us ever voting to include type aliases with this text in
the XPath Spec, because I would clearly remember voting against this.

Please, let us follow our standard procedures.

Thanks,

Dimitre