EDD rule that refers to the book element - impossible?

[Jakob Fix]

Hi, please consider this: I have a structured book with a large number
of components. The book structure conforms to the EDD, i.e. validating
the book works. The top element of the book, <book> has a @status
attribute that can be either "draft" or "publishable". In the
component files, I have xrefs that in draft mode are underlined. For
publishing, the underline should be removed.  My attempts to deal with
this via the EDD have so far been unsuccessful. Is this the right
approach?

For the xref element I've specified this rule:

Text format rules
  If context is: * < book[status=”draft”]
    Text range.
      Font properties
        Underline: Single
  Else
    Text range.
      Font properties
        Underline: None

But it doesn't seem to get picked up. The documentation (Structured
Application Developer's Guide) does not make any statements about the
(non-)permeability of the border between book component and the book
itself.

thanks,
Jakob.