Missing xmlns:xs declaration in house rules Schematron file

[galtm]

The xs prefix used in the line below isn't bound to its namespace.

oscal-xproc3/testing/xproc3-house-rules.sch

Line 49 in bb76ea1

<xsl:function name="ox:leads-with-variable-reference" as="xs:boolean">

In XML Calabash alpha 16, I get an error, which makes sense:

Error in xsl:function/@as in xproc3-house-rules.sch:
  XPST0081  Namespace prefix 'xs' has not been declared

In MorganaXProc 1.4.5, I get no error, even if I modify the schema so that the function gets called. I don't know if raising an error is implementation defined. (Cc: @xml-project)