How can I select an element with multiple classes with Xpath?

Question

In the above xml sample I would like to select all the books that belong to class foo and not in class bar by using xpath.

Answer 1

Although I like Mads solution: Here is another approach for XPath 2.0:

/bookstore/book[
                 tokenize(@class," ")="foo" 
                 and not(tokenize(@class," ")="bar")
               ]

Please note that the following expressions are both true:

("foo","bar")="foo" -> true
("foo","bar")="bar" -> true