anchor.diff:   . first reads and parses all files with '.xml' extension in 'flora' directory,
    . then collects all parsed documents into a new document whose document element is +<flora>...</flora>+,
    . then transforms this document with XSLT stylesheet 'flora/styles/to-genera.xsl',
  - . then finds all fragments from the resulted document which matches XPath criterion +/genera/genus+,
  + . then finds all fragments from the resulted document which matches XPath criterion +/genera/genus+ and inserts document type declarations like +<!DOCTYPE genus SYSTEM "genus.dtd">+ into them,
    . finally writes each fragment to a file whose path is 'flora-genera/XXX.xml', where +XXX+ is the string value of XPath expression +/genus/@name+ of each fragment document (that is, +XXX+ of the document element +<genus name="XXX">...</genus>+).
   
   Additionally, it might be noteworthy that:
  
positive.code: [options="header", cols="1,3,1"]
  |=================
  | Element | Description | Required
  |transform|A _Transform_ sink. .4+| No; at least one sink required
  |all|An _All_ sink.
  |snip|A _Snip_ sink.
  |output|An _Output_ sink.
  |=================
  
  
  [[actors.snip]]
  === Snip filter
  
negative.code:     <all root="flora">
        <transform style="flora/styles/to-genera.xsl">
          <snip select="/genera/genus">
            <doctype systemid="genus.dtd"/>
            <output destdir="flora/genera" refer="/genus/@name">
              <globmapper from="*" to="*.xml"/>
            </output>
  