xpath expression from xml with namespace prefix

Question

I could not get the following xpath expression to work when the xml path namespace prefix set.

/bk:BookStore/bk:Books/bk:Book[text()='Time Machine']

XML is:

<BookStore xmlns:bk="http://www.bookstore.com/book#">
  <bk:Books>
    <bk:Book id="1">Time Machine></bk:Book>
  </bk:Books>
</bk:BookStore>

Answer 1

Without more information about the host language (in which you attempt to evaluate XPath expressions) it is not possible to provide an useful recommendation.

Generally, one needs to "register" a namespace with a namespace manager and this also associates a prefix to the registered namespace. Then, using this NamespaceManager object as an argument to the XPath-evaluation method, one can specify as argument to this method an XPath expression that contains names prefixed by that particular prefix.

Workarounds:

/*/*[name()='bk:Books']/*[name()='bk:Book' and text()='Time Machine']

Answer 2

Or even better (and more portable), without the unnecessary prefix:

/*/*[local-name()='Books'] ... and so on

The function local-name ignores any prefix, which, as correctly stated by commenters, can vary.