Filtering out books with short description

Hello experts,

all my postings here relate to a number of problems regarding one set of
content I have to solve. I have a list of books (simplified to make our
lifes easier:). This content needs to be transformed for various purposes.

<bookshelf>
  <book>
    <title>First book</title>
    <description>text text text</description>
  </book>
  <book>
    <title>Second book</title>
    <description>text text</description>
  </book>
  <book>
    <title>Third book</title>
    <description>text</description>
  </book>
</bookshelf>

I would like to filter out all books with short descriptions. How can I do
that? I curretnly see two different ideas of how this could be done (text
lengh and number of text tokens) and wonder if you can help me with one or
perhaps even both of them?

1) Copy only books with a description text of at least 5 letters in the
resulting XML file. That would remove the third book. The result would only
contain the first and teh second book. How can I do that?

2) Copy only books with at least 3 text tokens in the description element.
After doing that only the first book would arrive in the resulting XML file.
Is there a way to do that with XSLT? I am using XALAN.

Kind Regards and many thanks in advance,
Karl

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