How to select a node using XPath if sibling node has a specific value?

Question

I have the following document:

  abc
  ccc
  
ffffd


  zz         


        

Answer 1

First off, your example is not well-formed XML. Overlooking that and that you didn't describe your intents very well (What exactly do you want to select on which condition?), I assume you want to do this:

//cc[preceding-sibling::bb[text()="zz"]]/text()

It selects

TEXT VALUES OF ALL  ELEMENTS
//cc                                    /text()
    THAT HAVE A PRECEDING SIBLING 
    [preceding-sibling::bb             ]
                          THAT HAS TEXT VALUE EQUAL TO "zz"
                          [text()="zz"]

You could write is also as

//bb[text()="zz"]/following-sibling::cc/text()

Please look at the spec, it has some very well readable examples from which you'll learn a lot.