Select node with unique id using XSLT

Question

How can I select a specific node with an unique ID and return the entire node as xml.

<xml>
<library>
<book id='1'>
<title>firstTitle</title>
<author>firstAuthor</author>
</book>
<book id='2'>
<title>secondTitle</title>
<author>secondAuthor</author>
</book>
<book id='3'>
<title>thirdTitle</title>
<author>thirdAuthor</author>
</book>
</library>
</xml>

In this case I would like to return book with id='3', so it will look something like this:

<book id='3'>
<title>thirdTitle</title>
<author>thirdAuthor</author>
</book>

Answer 1

If you are referring to XPath (because you are searching in the document, not transforming it), that would be:

//book[@id=3]

Of course, depending on your language, there might be a library that makes this search even simpler.