Including node in group when grouping key is null

Hi, all...

Question about xsl:for-each-group, if you please:

In my DITA bookmap, I have this code to output different lists of primary
authors, contributing authors, and contributors:

<xsl:for-each-group select="author" group-by="@type">
...
</xsl:for-each-group>

The type attribute value indicates whether the author is primary,
contributing, or other (contributor).

Is there a way to process an author element that is missing the type
attribute? That is, if a bookmap creator neglects to specify the type
attribute for an author, I'd like to list it among the primary authors. I'm
referring to the case where the @type is missing, not present but a null
string.

Can anyone provide guidance?

Thx

Steve


Steve Fogel | Information Architect, Oracle Database | 650.506.4914
Oracle Server Technologies Information Development
500 Oracle Parkway | M/S 4op1126 | Redwood Shores, CA 94065