Our implementation disagrees with the expected (empty sequence) result for test FTNot-q6.

(: FTNot-q6: violates negation restriction 2: FTST0002 possible :)

(: insert-start :)
declare variable $input-context external;
(: insert-end :)

(: nothing :)
$input-context/books/book[para contains text "software" ftand ("coder" ftand ftn
ot
"ninja" window 5 words)]/title

Consider the paragraph:

   <para>Amazingly enough, many people believe that nunchuks are not useful
    to software development! They prefer usability studies to the swift
    application of physical means of persuasion. Hah! The ninja coder knows
    otherwise.
    </para>

and the predicate

para contains text "software" ftand ("coder" ftand ftnot "ninja" window 5 words

Indexing word positions at 1, 'ninja' is at position 29 (a StringExclude) and 'coder' is at 30 (a StringInclude).

Using the function fts:ApplyFTWordWindow  at 

http://www.w3.org/TR/xpath-full-text-10/#tq-ft-fs-FTWindow

n = 5
minpos = 30
maxpos = 30
windowStartPos ranges from 26 to 30 (inclusive)

When windowStartPos is 30, windowEndPos is 34.

Thus:

         for $stringExclude in $match/fts:stringExclude
            where $stringExclude/fts:tokenInfo/@startPos >=
                  $windowStartPos
              and $stringExclude/fts:tokenInfo/@endPos <=
                  $windowEndPos
            return $stringExclude

returns the empty sequence, because 

$stringExclude/fts:tokenInfo/@startPos = 29 which is less than the windowStartPos, thus there exists a window starting at the word 'coder' which doesn't include 'ninja'.  The match contains no stringExcludes so gives the query a result of <title>Ninja Coder</title>.