The W3C has published a proposed edited recommendation of XML Base (Second Edition). The most significant change is the addition of a section on "Interpretation of same-document references":
RFC 3986 defines certain relative URI references, in particular the empty string and those of the form
#fragment, as same-document references. Dereferencing of same-document references is handled specially. However, their use as the value of an
xml:baseattribute does not involve dereferencing, and XML Base processors should resolve them in the usual way. In particular,
xml:base=""does not reset the base URI to that of the containing document.
Some existing processors do treat these
xml:basevalues as resetting the base URI to that of the containing document, so the use of such values is strongly discouraged.
I think that XOM is one of the processors that does treat
xml:base="" as resetting the base URI. I'll have to look into that.
The question that arises is whether there should be a way to reset the base URI to that of the containing document.