> not that it will happen to you but its a best practice to 
> refer a text value 
> of a node by text(). 
> 
> <xsl:a-t select="book[owner/text()='aaa' or 
> chapter/owner/text()='aaa']"/>
> 

No, this is absolutely *not* recommended. If you use /text(), your code will
be sensitive to the presence of comments within the text, and it's very
unusual that you should want comments to make any difference.

owner='aaa' compares the string value of the owner element against the
string 'aaa'. If the owner element is

<owner>aa<!--three stars-->a</owner>

then owner='aaa' will succeed, but owner/text() will fail.

Michael Kay
http://www.saxonica.com