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<?xml version="1.0"?>
<!DOCTYPE appendix
  PUBLIC "-//OASIS//DTD DocBook V4.2//EN"
         "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">

<book>
  <title>Change Log For The YAML 1.0 Specification</title>
  <subtitle>Last Updated On 2005-01-18</subtitle>

  <chapter>
    <title>Changes From The 28 Dec 2004 Draft</title>

    <variablelist>
      <varlistentry>
        <term><para>
          Break Syntax Chapter
        </para></term>
        <listitem><para>
          As proposed by Rich Morin.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>
          Nit Fixes
        </para></term>
        <listitem><para>
          A lot of nits detected by Rich Morin, Tichy Braoo and Alexis Layton.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>
          Broken Links
        </para></term>
        <listitem><para>
          Several broken links detected by Tichy Braoo.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>
          Break Syntax Chapter
        </para></term>
        <listitem><para>
          To several smaller chapters.
        </para></listitem>
      </varlistentry>

    </variablelist>
  </chapter>

  <chapter>
    <title>Changes From The 15 Mar 2003 4th Last Call Draft</title>

    <variablelist>
      <varlistentry>
        <term><para>
          Boolean canonicals
        </para></term>
        <listitem><para>
          Change to
          <quote><userinput>y</userinput></quote>/<quote><userinput>n</userinput></quote>.
          Remove
          <quote><userinput>+</userinput></quote>/<quote><userinput>-</userinput></quote>
          from examples and the bool type definition. This should have been
          done a while back (when a plain value could no longer be
          <quote><userinput>-</userinput></quote>).
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>
          Time-less dates
        </para></term>
        <listitem><para>
          Changed to 00:00:00Z instead of 12:00:00Z.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>
          Renamed <userinput>!special</userinput> to
          <userinput>!yaml</userinput>
        </para></term>
        <listitem><para>
          Better reflects the intent.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>DocBook format</para></term>
        <listitem><para>
          To allow for easier media retargeting. Support HTML and PDF (using
          XEP).
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Fix production bugs</para></term>
        <listitem><para>
          Prevent header/trailer from appearing as content - Thanks to Robin
          Green for catching this one.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>
          Change <quote>Serialization</quote> back to <quote>Document</quote>
        </para></term>
        <listitem><para>
          By popular demand.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Implicit/explicit indentation</para></term>
        <listitem><para>
          Allow leading empty lines, and indented content lines to start with a
          <quote><userinput>#</userinput></quote> character.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>
          Changed <quote><userinput>taguri:</userinput></quote> to
          <quote><userinput>tag:</userinput></quote>
        </para></term>
        <listitem><para>
          As per the updated tag URI RFC.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>YAML Processor</para></term>
        <listitem><para>
          Used the term <quote>(YAML) processor</quote> instead of parser,
          loader etc. This avoids forcing preconcieved notions on system
          architecture to affect the semantics.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Rearranged and renamed node/value productions</para></term>
        <listitem><para>
          Hopefully this would increase production readability.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Hungarian explained</para></term>
        <listitem><para>
          Add a note explaining the production prefixes.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Status</para></term>
        <listitem><para>
          Changed to release candidate.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Allow inline collection form in complex keys</para></term>
        <listitem><para>
          Reusing the productions from the *-in-seq form.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Allow omitting complex and flow keys values</para></term>
        <listitem><para>
          Allows for a nicer set notation.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>
          Allow implicit single pair maps in flow sequences
        </para></term>
        <listitem><para>
          Allows for a nicer ordered map connection.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Major re-write of model and intro chapters</para></term>
        <listitem><para>
          Add figures, rephrase, make more readable.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>URI escaping</para></term>
        <listitem><para>
          Gone.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Empty plain scalars</para></term>
        <listitem><para>
          Are forbidden as keys and as flow sequence entries.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Trailing commas</para></term>
        <listitem><para>
          Are allowed in flow collections and following ... line. Empty lines
          ending with a specific line break are now treated as comments even
          if following a block scalar.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Folding and Chomping</para></term>
        <listitem><para>
         Rules have been massively simplified.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Examples</para></term>
        <listitem><para>
         Completely new examples set, with highlights associating parts of the
         characters stream with specific productions.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Productions</para></term>
        <listitem><para>
         Re-work almost all productions in the syntax section, together with
         examples.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Sam&#8217;s corrections</para></term>
        <listitem><para>
         Incorporated minor wording issues (thanks to Sam Vilain).
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>
          YAML 1.1
        </para></term>
        <listitem><para>
          New directive syntax, %TAG directives, patched indentation rules,
          moved !!str, !!seq and !!map to the repository. Hopefully this is the
          last "global" change.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>
          Index
        </para></term>
        <listitem><para>
          Replace all internal links with index entries. It is simply amazing
          how much work is expressed in this short sentence.
        </para></listitem>
      </varlistentry>
    </variablelist>
  </chapter>

  <chapter>
    <title>Changes From The 24 Jan 2003 3rd Last Call Draft</title>

    <variablelist>
      <varlistentry>
        <term><para>Implicit header</para></term>
        <listitem><para>
          Was changed to <quote>---</quote> instead of <quote>---
          %YAML:1.0</quote>.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Implicit document</para></term>
        <listitem><para>
          Now allows all collection styles, not only block collections.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Block sequence indentation</para></term>
        <listitem><para>
          Wording, productions and examples fixed to allow for more
          human-friendly interpretation of <quote>-</quote> as indentation.
        </para></listitem>
      </varlistentry>
    </variablelist>
  </chapter>

  <chapter>
    <title>Changes From The 31 Oct 2002 2nd Last Call Draft</title>

    <variablelist>
      <varlistentry>
        <term><para>BNF productions</para></term>
        <listitem><para>
          Were renamed with a hungarian-like prefix notation and reformatted so
          that cut-and-paste from HTML would yield proper results.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Vocabulary instead of language</para></term>
        <listitem><para>
          The term <quote>vocabulary</quote> better describes the intent of
          sub-domains of yaml.org (for type families).
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Seq-in-seq</para></term>
        <listitem><para>
          Was added (similar to map-in-seq).
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Throwaway indicator</para></term>
        <listitem><para>
          Changed from <quote><userinput> # </userinput></quote> to
          <quote><userinput> #</userinput></quote>.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Directive indicator</para></term>
        <listitem><para>
          Changed from <quote><userinput>#</userinput></quote> to
          <quote><userinput>%</userinput></quote>.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Anchors and directive names</para></term>
        <listitem><para>
          Can be any non-space flow char.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Flow values</para></term>
        <listitem><para>
          May start on a following line.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>
          Special <quote><userinput>-</userinput></quote> plain value
        </para></term>
        <listitem><para>
          Is canceled (ambiguous with next-line flow). Therefore the
          <userinput>-/+</userinput> Boolean implicits are gone as well.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Language-independent types</para></term>
        <listitem><para>
          Corrected date indicators.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Integers and floats</para></term>
        <listitem><para>
          Added sexagesimal (base 60) format (using
          <quote><userinput>:</userinput></quote>) for time (and degrees).
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Nulls</para></term>
        <listitem><para>
          Removed the <quote><userinput>Undef</userinput></quote> possibility.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Merge</para></term>
        <listitem><para>
          Changed from <quote><userinput>&lt;=</userinput></quote> to
          <quote><userinput>&lt;&lt;</userinput></quote>.
        </para></listitem>
      </varlistentry>
    </variablelist>
  </chapter>

  <chapter>
    <title>Changes From The 01 sep 2002 1st Last Call Draft</title>

    <variablelist>
      <varlistentry>
        <term><para>Brian&#8217;s wording fixes</para></term>
        <listitem><para>
          Spelling and minor re-wording.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para><userinput>#TAB</userinput> was removed</para></term>
        <listitem><para>
          Tabs are now completely banned from indentation.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Escaping of type family name</para></term>
        <listitem><para>
          The interaction between <quote><userinput>\</userinput></quote> and
          <quote><userinput>%</userinput></quote> escaping has been clarified
          in a better way.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Zero explicit indentation</para></term>
        <listitem><para>
          Is now allowed for top level nodes.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Moved language-independent types out of the spec.</para></term>
        <listitem><para>
          Only !map, !seq and !str are in it now.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Changed implicit types</para></term>
        <listitem><para>
          No longer require (). Implicit empty string is !null. Changed nil to
          undef. These changes depend on a resolution to the implicit typing
          issues; hence all the separate type documents are not in <quote>last
          call</quote> status. Yet.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Changed NULL escape</para></term>
        <listitem><para>
          From \z to \0.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>
          Changed <quote><userinput>-</userinput> entry</quote> indentation
        </para></term>
        <listitem><para>
          Consider the <quote><userinput>-</userinput></quote> to be
          indentation, but not the following spaces.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>
          Changed format separator to <quote><userinput>#</userinput></quote>
        </para></term>
        <listitem><para>
          This makes transfer methods into URI-references (allow fragments).
          Type families are URIs (without fragments).
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Mutability == collection</para></term>
        <listitem><para>
          Make all collections mutable and all scalars immutable. This
          simplifies generic tools and the native model.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Re-ordered sections</para></term>
        <listitem><para>
          Moved information models to the end.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Graph implicit types</para></term>
        <listitem><para>
          Allow types to remain unknown (implicit) all the way up to and
          including the graph model; allow implicit collection types.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Graph implicit types</para></term>
        <listitem><para>
          Allow types to remain unknown (implicit) all the way up to and
          including the graph model; allow implicit collection types.
        </para></listitem>
      </varlistentry>
    </variablelist>
  </chapter>

  <chapter>
    <title>Changes From The 10 Jul 2002 Draft</title>

    <variablelist>
      <varlistentry>
        <term><para>Status</para></term>
        <listitem><para>
          Was changed to <quote>Last Call</quote>. At long last.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Implicit strings</para></term>
        <listitem><para>
          May begin with a <quote><userinput>/</userinput></quote> to allow
          paths to be unquoted.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Removed the <userinput>//</userinput> special keys.</para></term>
        <listitem><para>
          They conflict with the new implicit string format. What to replace
          them with, if anything, is still TBD.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Example fixes</para></term>
        <listitem><para>
          Minor nits were wrong in some examples (4.3.1, 4.6.4, 4.6.5, 4.6.7).
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>
          Renamed <quote>public</quote> type families to <quote>global</quote>
        </para></term>
        <listitem><para>
          This better conveys the intent.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Separated changes</para></term>
        <listitem><para>
          As of this draft, changes are in a separated document.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Repaginated draft</para></term>
        <listitem><para>
          The previous pagination was nice but it was very wasteful of pages.
          In the spirit of keeping the spec small, page breaks were moved,
          reducing the printed size by 10 pages or so.
        </para></listitem>
      </varlistentry>
    </variablelist>
  </chapter>

  <chapter>
    <title>Changes From The 06 Jul 2002 Draft</title>

    <variablelist>
      <varlistentry>
        <term><para>Table of content</para></term>
        <listitem><para>
          Was enhanced to specify page numbers as well as links. Also, entry
          3.1.4 was missing.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Section 1.2, paragraph 7</para></term>
        <listitem><para>
          Remove the sentence about indentation being used for multiple
          documents (it isn&#8217;t).
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Syntactical problems</para></term>
        <listitem><para>
          Using <quote>an flow</quote> (leftover from the global substitute)
          and various other minor fixes.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Renamed <quote>nested</quote> to <quote>block</quote></para></term>
        <listitem><para>
          In all the wording. This makes the wording match the productions.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Cleaned canonical formats</para></term>
        <listitem><para>
          In some cases, the canonical format was a subset of another format,
          rather than being an implicit format on its own. This is allowed, and
          is now explicit in the format definition. Also fixed the string
          formats to satisfy the requirement that a value would only match one
          implicit or explicit format.
        </para></listitem>
      </varlistentry>
    </variablelist>
  </chapter>

  <chapter>
    <title>Changes From The 30 Jun 2002 Draft</title>
    <variablelist>
      <varlistentry>
        <term><para>Printing</para></term>
        <listitem><para>
          Should be much improved. Explicit page breaks were added and some
          reorganization was done so that breaks should reflect logical chunks.
          At least in A4 and Letter pages size on IE6 :-)
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Productions 94 and 98</para></term>
        <listitem><para>
          Now reflect the correct indentation policy for map-in-seq.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Productions 129 and 130</para></term>
        <listitem><para>
          Were renamed to <quote>folded-paragraph</quote> and
          <quote>folded-text-line</quote> to better reflect the intent.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>
          The <quote><userinput>...</userinput></quote> <quote>pause</quote>
          marker
        </para></term>
        <listitem><para>
          Was added as per the discussions in the mailing list. This added two
          productions.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Examples</para></term>
        <listitem><para>
          Some examples were re-worked as part of the re-organization.
          Hopefully for the better. The XML example was removed.
        </para></listitem>
      </varlistentry>
    </variablelist>
  </chapter>

  <chapter>
    <title>Changes From The 25 Jun 2002 Draft</title>

    <variablelist>
      <varlistentry>
        <term><para>Printing enhancements</para></term>
        <listitem><para>
          Add page-break in many locations for better printing, make table of
          contents two columns.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Terminology</para></term>
        <listitem><para>
          <para>
            Change <quote>block scalar</quote> to <quote>literal
            scalar</quote>, change <quote>in-line</quote> to
            <quote>flow</quote>. This allows for two sorts of mechanisms, the
            <quote>block</quote> mechanism and the <quote>flow</quote>
            mechanism. Within block are literal and folded scalars; within flow
            are plain, single, and double. This involved a few global
            substitutions which will probably introduce error, those are:
          </para>

          <itemizedlist>
            <listitem><para>s/in-line/flow/</para></listitem>
            <listitem><para>s/nest-/blk-/</para></listitem>
            <listitem><para>s/line-/flow-/</para></listitem>
            <listitem><para>s/flow-feed/line-feed</para></listitem>
            <listitem><para>s/flow-separator/line-separator</para></listitem>
            <listitem><para>s/flow-break-char/line-break-char</para></listitem>
            <listitem><para>s/flow-break/break</para></listitem>
          </itemizedlist>
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Preview Re-structuring</para></term>
        <listitem><para>
          Restructure the preview section for general readability.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Production Changes</para></term>
        <listitem><para>
          Minor change to the comment-break production
        </para></listitem>
      </varlistentry>
    </variablelist>
  </chapter>

  <chapter>
    <title>Changes From The 14 Jun 2002 Draft</title>

    <variablelist>
      <varlistentry>
        <term><para>Use (word) instead of .word for <quote>enums</quote></para></term>
        <listitem><para>
          This is going to be our generic way to handle implicits that
          otherwise would be taken to be strings.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>
          Change <quote>word</quote> format names to <quote>english</quote>
        </para></term>
        <listitem><para>
          More correctly reflects their semantics.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Canonical Booleans</para></term>
        <listitem><para>
          Change canonical Booleans to <userinput>+/-</userinput>. Had to
          make a special case to allow <quote><userinput>-</userinput></quote>
          in unquoted values to do it. This doesn&#8217;t apply to keys, but using
          the English format there makes more sense anyway. This allows
          canonical boolean to be implicit.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Add (null)/(nil)</para></term>
        <listitem><para>
          In addition to <userinput>~</userinput>, consistent with booleans.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Unify date/time</para></term>
        <listitem><para>
          Merge them into timestamp (and rename it to <quote>time</quote>).
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Relax string regexp</para></term>
        <listitem><para>
          Anything starting with a <quote>text</quote> character
          (<quote><userinput>-</userinput></quote>, letter or digit),
          except for int/flt/time.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Change space escapes</para></term>
        <listitem><para>
          <quote><userinput>\ </userinput></quote> is now a space,
          <quote><userinput>\-</userinput></quote> is now NBSP.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Allow repeated <userinput>#</userinput></para></term>
        <listitem><para>
          To begin throwaway comments.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Renamed the three chomping variants</para></term>
        <listitem><para>
          To <quote>strip</quote>, <quote>clip</quote> (default) and
          <quote>keep</quote>.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Changed in-line folding</para></term>
        <listitem><para>
          To allow empty lines to represent line feeds and to preserve specific
          line breaks. The WIKI feature isn&#8217;t included as it depends on
          indentation.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Changed simple style</para></term>
        <listitem><para>
          To reflect the new restrictions (keys can&#8217;t span; in-lines can&#8217;t have
          <quote><userinput>, </userinput></quote> and <quote><userinput>:
          </userinput></quote>; for top-level values, anything goes except
          comments. Comments can no longer be interleaved in such scalars.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>
          Make <quote><userinput>?</userinput></quote> into a space separator
        </para></term>
        <listitem><para>
          No reason not to. It was always followed by a space anyway.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Renamed scalar styles</para></term>
        <listitem><para>
          Rename <quote>plain</quote> to <quote>block</quote> and
          <quote>simple</quote> to <quote>plain</quote>. As a result of the
          above it isn&#8217;t that simple any more <userinput>:-)</userinput> and
          having both <quote>plain</quote> and <quote>simple</quote> was
          confusing. Reverting to <quote>block</quote> more accurately reflects
          the semantics, freeing <quote>plain</quote> for the unquoted style.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Renamed productions</para></term>
        <listitem><para>
          To make the document more printer-friendly. The main change was to
          rename <userinput>nested-</userinput> to
          <userinput>nest-</userinput> and
          <userinput>inline-</userinput> to
          <userinput>line-</userinput>. The latter is particularly painful,
          but there was no other good choice.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Float round-tripping</para></term>
        <listitem><para>
          Added a warning that float values may not round-trip exactly due to
          the use of native float data types.
        </para></listitem>
      </varlistentry>
    </variablelist>
  </chapter>

  <chapter>
    <title>Changes From The 27 May 2002 Draft</title>
    <variablelist>
      <varlistentry>
        <term><para>Provide mailing list URL</para></term>
        <listitem><para>
          So that its address would be clear even from the printed version.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Line Processing section</para></term>
        <listitem><para>
          Was renamed <quote>Space processing</quote>.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Document productions</para></term>
        <listitem><para>
          Were cleaned up and now allow comments before the header line.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Printing</para></term>
        <listitem><para>
          Many tweaking to ensure printing doesn&#8217;t clip the comments of the
          productions tables.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Float format</para></term>
        <listitem><para>
          Extended to allow for infinity and not a number.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Block indicators</para></term>
        <listitem><para>
          Changed to <userinput>|</userinput>, <userinput>&gt;</userinput> and
          <userinput>\</userinput> (without the leading
          <userinput>|</userinput>).
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Information model</para></term>
        <listitem><para>
          Whole section was re-worked to accommodate the latest decisions in
          the mailing list. Leaf and branch are now renamed to collection and
          scalar; keyed and series are renamed to mapping and sequence.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Multi-line in-lines</para></term>
        <listitem><para>
          Are now allowed, including multi-line in-line scalars.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Limit implicit strings</para></term>
        <listitem><para>
          To word and space characters only.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Unreserve <userinput># % ^</userinput></para></term>
        <listitem><para>
          No need to reserve them - they can&#8217;t be used as first characters in a
          simple value anyway because there&#8217;s no implicit type using them.
          Unreserving them allows them to be used in implicit types in the
          future.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Modify folding</para></term>
        <listitem><para>
          To preserve line breaks around more-indented and specific empty
          lines.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Spell checking</para></term>
        <listitem><para>
          Run the whole document throught Word for spell checking.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Model chart</para></term>
        <listitem><para>
          Changed to use style sheet in a more dependable way, and now reflects
          the fact the native and generic models <quote>are one</quote> in some
          respects.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Wording for String</para></term>
        <listitem><para>
          Changed to reflect the fact
          <quote><userinput>-</userinput></quote> isn&#8217;t a word character.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Chomp control</para></term>
        <listitem><para>
          Was added (<quote><userinput>-</userinput></quote> for chomp,
          <quote><userinput>+</userinput></quote> for keep).
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Escaped nested style</para></term>
        <listitem><para>
          Was removed. It is redundant due to <quote>..</quote> spanning lines.
        </para></listitem>
      </varlistentry>
    </variablelist>
  </chapter>

  <chapter>
    <title>Changes From The 28 Apr 2002 Draft</title>
    <variablelist>
      <varlistentry>
        <term><para>Explicit Syntax</para></term>
        <listitem><para>
          Explicit notation is now required for empty scalars. This reverts the
          change in the previous draft.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>No alternate style for collections.</para></term>
        <listitem><para>
          Map and seq can now only be written in keyed and series style.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Comments</para></term>
        <listitem><para>
          Are now allowed to trail lines except for inside multi line text.
          Comments (explicit and implicit) may trail multi-line text values as
          long as they are less indented.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>URI Scheme</para></term>
        <listitem><para>
          Is now correctly limited to word characters.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Trailing comma</para></term>
        <listitem><para>
          Is no longer allowed in in-line collections.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Simple char</para></term>
        <listitem><para>
          Production 170 fixed to prohibit in-line indicators after a space
          indicator, or two space indicators followed by a space.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Base64 Format</para></term>
        <listitem><para>
          Was listed as <quote>canonical</quote>. Fixed to
          <quote>explicit</quote>.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Time intro examples</para></term>
        <listitem><para>
          Used the wrong format
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Production fixes</para></term>
        <listitem><para>
          Correct minor problems (missing <quote>(n)</quote>, improper handling
          of spaces in in-line collections, missing
          <quote><userinput>|</userinput></quote>, etc.)
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Integer and Float formats</para></term>
        <listitem><para>
          Now ignores any <quote><userinput>,</userinput></quote> inside the
          value. This required making <quote><userinput>,</userinput></quote>
          into a space separator.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Boolean</para></term>
        <listitem><para>
          Is now a type of its own.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Ptr</para></term>
        <listitem><para>
          Was removed. Will probably be a Perl-specific type.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Leaf styles</para></term>
        <listitem><para>
          Were simplified to only 6 (3 nested and 3 in-line).
        </para></listitem>
      </varlistentry>
    </variablelist>
  </chapter>

  <chapter>
    <title>Changes From The 07 Apr 2002 Draft</title>
    <variablelist>
      <varlistentry>
        <term><para>Document Separator</para></term>
        <listitem><para>
          Is now restricted to <quote><userinput>---</userinput></quote>. BOM
          is allowed if encoding does not change. Production 49 has been
          corrected accordingly, and the reference to the obsolete
          <userinput>non-alias_node</userinput> was corrected.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>In-series keyed</para></term>
        <listitem><para>
          This special case (production 93) has been restricted to in-line leaf
          keys without any properties. This minimizes lookahead in parsers.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Inline leaf</para></term>
        <listitem><para>
          Now allows an empty unquoted value (production 163).
        </para></listitem>
      </varlistentry>
    </variablelist>
  </chapter>

  <chapter>
    <title>Changes From The 10 Mar 2002 Draft</title>

    <variablelist>
      <varlistentry>
        <term><para>Anchors for aliases</para></term>
        <listitem><para>
          Are now forbidden.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Timestamp format</para></term>
        <listitem><para>
          Fixed a problem with the regexp. Allow both a valid ISO8601 format
          (using <quote><userinput>T</userinput></quote>) and a space separated
          format (for readability).
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Productions</para></term>
        <listitem><para>
          Break node productions to smaller bits.
        </para></listitem>
      </varlistentry>
    </variablelist>
  </chapter>

  <chapter>
    <title>Changes From The 20 Feb 2002 Draft</title>

    <variablelist>
      <varlistentry>
        <term><para>YAC 22</para></term>
        <listitem><para>
          The <userinput>#TAB</userinput> directive is now required to allow
          tabs in indentation.
        </para></listitem>
      </varlistentry>
    </variablelist>
  </chapter>

  <chapter>
    <title>Changes From The 16 Feb 2002 Draft</title>

    <variablelist>
      <varlistentry>
        <term><para>Corrected examples</para></term>
        <listitem><para>
          Floating point numbers in all examples now start with
          <quote><userinput>0</userinput></quote>.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Wording improvements</para></term>
        <listitem><para>
          In various places.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Empty line indentation</para></term>
        <listitem><para>
          Is now be <userinput>indent(&lt;=n)</userinput> instead of the
          previous <userinput>indent(n)?</userinput>
        </para></listitem>
      </varlistentry>
    </variablelist>
  </chapter>

  <chapter>
    <title>Changes From The 10 Feb 2002 Draft</title>

    <variablelist>
      <varlistentry>
        <term><para>YAC 20</para></term>
        <listitem><para>
          The yaml: scheme has been replaced by an http: one. Mapping of XML
          namespaces is now done using <quote><userinput>$</userinput></quote>
          instead of <quote><userinput>;</userinput></quote>. The prefix
          indicator is now <quote><userinput>^</userinput></quote> and the
          format indicator is now <quote><userinput>|</userinput></quote>.
        </para></listitem>
      </varlistentry>
    </variablelist>
  </chapter>

  <chapter>
    <title>Changes From The 10 Dec 2001 Draft</title>

    <variablelist>
      <varlistentry>
        <term><para>Transfer Method</para></term>
        <listitem><para>
          Is now split to type family and format; type family is now a URI.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Date/Time Types</para></term>
        <listitem><para>
          Were added.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Tree Model</para></term>
        <listitem><para>
          Now includes the format.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Wording changes</para></term>
        <listitem><para>
          Throughout the whole spec.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Format in Transfer Method</para></term>
        <listitem><para>
          Is now separated by a <quote><userinput>`</userinput></quote>.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>YAC List</para></term>
        <listitem><para>
          Removed the Probable changes section; it is now replaced by the YAC
          list.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>YAC 3, YAC 5</para></term>
        <listitem><para>
          Added a uniform URI based namespace scheme.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>YAC 6</para></term>
        <listitem><para>
          Unrecognized explicitly typed implicit (simple) leafs are allowed.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>YAC 7</para></term>
        <listitem><para>
          C1 Control codes are explicitly forbidden.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>YAC 10</para></term>
        <listitem><para>
          In-series in-line syntax was modified according to the flexible
          indentation scheme (YAC needs to be updated).
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>YAC 11</para></term>
        <listitem><para>
          Rename implicit leaves to simple leaves.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>YAC 12</para></term>
        <listitem><para>
          Throwaways are now allowed everywhere. Blank lines are comments.
          <emphasis>There are ambiguity problems in chomped leaf
          values.</emphasis>
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>YAC 13</para></term>
        <listitem><para>
          Indentation is now generic (flexible).
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>YAC 14</para></term>
        <listitem><para>
          Nested leaf format is now built out of three orthogonal properties.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>YAC 15</para></term>
        <listitem><para>
          Top level nodes can be in-line.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>YAC 16</para></term>
        <listitem><para>
          A <quote><userinput>--- #YAML:1.0</userinput></quote> is assumed if
          there&#8217;s no header.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>YAC 18</para></term>
        <listitem><para>
          YAML Ain&#8217;t Markup Language
        </para></listitem>
      </varlistentry>
    </variablelist>
  </chapter>

  <chapter>
    <title>Changes From The 11 Nov 2001 Draft</title>

    <variablelist>
      <varlistentry>
        <term><para>Quoted Strings</para></term>
        <listitem><para>
          Are now implemented as a text implicit transfer format. This changed
          slightly the definition of an escaped leaf so that the two would be
          equivalent.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Relative DNS type familys</para></term>
        <listitem><para>
          Are now supported using the simplest form only. the definition of an
          escaped leaf so that the two would be equivalent.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Syntax/Grammar/Formatting</para></term>
        <listitem><para>
          Were fixed according to Brian&#8217;s inputs.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Block</para></term>
        <listitem><para>
          Is now chomped using <quote><userinput>||</userinput></quote> rather
          than <quote><userinput>|-</userinput></quote> for consistency.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Document Header</para></term>
        <listitem><para>
          Can now be anything starting with
          <quote><userinput>--</userinput></quote>; therefore is required
          before the first document in a multi-document stream.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Transfer Methods</para></term>
        <listitem><para>
          Can now accept any printable characters, not just words.
          <quote><userinput>!</userinput></quote> now means <quote>force
          implicit typing</quote>.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>New Scalar Styles</para></term>
        <listitem><para>
          We now have the following: <userinput>| || \ \\ ' "</userinput>
          implicit.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Treat sequence/map as Collection Styles</para></term>
        <listitem><para>
          In productions and in information model.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Add Structured Keys</para></term>
        <listitem><para>
          Using a key indicator (done - Oren).
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Add Examples</para></term>
        <listitem><para>
          Added a detailed examples section to the introduction to better
          acquaint the user so that the spec can proceed with some basic
          knowledge.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>In-line maps/sequences</para></term>
        <listitem><para>
          Are now supported. Empty maps/sequences are a natural special case.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Minor Changes</para></term>
        <listitem><para>
          Moved list of changes down... it was cluttering the top of the spec.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Information model and Preview</para></term>
        <listitem><para>
          Completely new rewrite.
        </para></listitem>
      </varlistentry>
    </variablelist>
  </chapter>

  <chapter>
    <title>Changes From The 04 Nov 2001 Draft</title>

    <variablelist>
      <varlistentry>
        <term><para>Polish</para></term>
        <listitem><para>
          Minor wording fixes, added internal links, etc.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>List</para></term>
        <listitem><para>
          Was renamed to <quote>sequence</quote>.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Separator</para></term>
        <listitem><para>
          Was changed to <quote>---</quote> instead of <quote>----</quote>.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Indentation</para></term>
        <listitem><para>
          Was changed to one space instead of one tab.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Base64</para></term>
        <listitem><para>
          Is no longer an implicit type. The surrounding
          <quote><userinput>[=...=]</userinput></quote> are kept,
          however, in case we change our mind later (e.g., if we introduce
          pipelining). The type was renamed to <quote>binary</quote> to stress
          its class rather than the encoding used.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Float</para></term>
        <listitem><para>
          Was renamed to <quote>real</quote> to decouple it from specific
          in-memory representation. Mathematicians may object :-)
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Length</para></term>
        <listitem><para>
          Was removed from the sequence map.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Type vs. Class</para></term>
        <listitem><para>
          Added some wording to clarify the difference. Most likely this will
          need to be changed once we settle the pipelining issue.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Productions</para></term>
        <listitem><para>
          Were completely overhauled, again, to accomodate the new semantics.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Next Line Scalars</para></term>
        <listitem><para>
          Now have two separate indicators, one for quoted and one for unquoted
          values.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Duplicate keys</para></term>
        <listitem><para>
          Are now an error. The parser may ignore the second occurrence with a
          warning.
        </para></listitem>
      </varlistentry>
    </variablelist>
  </chapter>

  <chapter>
    <title>Changes From The 12 Aug 2001 Draft</title>

    <variablelist>
      <varlistentry>
        <term><para>Indentation</para></term>
        <listitem><para>
          Has been changed to use tabs instead of spaces.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Throwaway comments</para></term>
        <listitem><para>
          Were added. The persistent comment key was changed to
          <quote><userinput>//</userinput></quote>.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Indicators</para></term>
        <listitem><para>
          Were changed. <quote><userinput>-</userinput></quote> now signifies a
          list entry and <quote><userinput>\</userinput></quote> signifies a
          next-line leaf value. <quote><userinput>@</userinput></quote> and
          <quote><userinput>%</userinput></quote> are no longer necessary (they
          may be if we ever support map/list keys). As a result no lookahead is
          ever required.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Multiple documents</para></term>
        <listitem><para>
          Are now possible in a single file (again), using
          <quote><userinput>----</userinput></quote> as a separator.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Wording</para></term>
        <listitem><para>
          Has been changed in numerous locations, hopefully to make it clearer.
          There was also some shuffling of the text sections to remove
          redundancy.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Productions</para></term>
        <listitem><para>
          Were thoroughly overhauled and therefore undoubtedly contain new
          bugs. Also, all the shorthand production names were replaced by long
          ones to improve readability.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Indicator keys</para></term>
        <listitem><para>
          Are no longer allowed. Structure keys are used instead, where some
          have only an in-memory representation.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Map/List keys</para></term>
        <listitem><para>
          Are no longer allowed. This may have to be revisited when Perl 6
          comes out.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Deep References</para></term>
        <listitem><para>
          Are still supported but as an explicit type rather than as a hack.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Types List</para></term>
        <listitem><para>
          Has been shrunk to only the common types, with a reference to
          yaml.org for a fuller list of types. The three core types were added
          as required types.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Type vs. Kind</para></term>
        <listitem><para>
          This distinction was inserted explicitly into the text, with several
          examples to drive the point home.
        </para></listitem>
      </varlistentry>
    </variablelist>
  </chapter>

  <chapter>
    <title>Changes From The 01 Aug 2001 Draft</title>

    <variablelist>
      <varlistentry>
        <term><para>Character Set</para></term>
        <listitem><para>
          Is now defined as simply printable Unicode characters without
          explicit ranges. This makes the spec resistant to the evolution of
          the Unicode spec.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Reserved Indicators</para></term>
        <listitem><para>
          The set of such indicators has been minimized. There is now a
          conflict between reserving them for future use and allowing people to
          use them as markers for implicit leaf types.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Simple Scalar</para></term>
        <listitem><para>
          Has been renamed to unquoted leaf.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Generic Model</para></term>
        <listitem><para>
          Has been generalized to allow for types nodes.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Implicit Typing</para></term>
        <listitem><para>
          Has been added with an assortment of suggested types.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>General Keys</para></term>
        <listitem><para>
          Keys can now be any nodes to allow for Java serialization.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Multi-level references</para></term>
        <listitem><para>
          Are now supported for Perl serialization.
        </para></listitem>
      </varlistentry>
    </variablelist>
  </chapter>
  <chapter>
    <title>Changes From The 31 Jul 2001 Draft</title>

    <variablelist>
      <varlistentry>
        <term><para>Simple Scalar and End Of Lines</para></term>
        <listitem><para>
          Moved eol productions to the end, rather than the start, of most
          productions. The wording and productions for the simple leaf were
          fixed to match each other and the intended semantics. The simple leaf
          example set was enhanced to clarify the proper interpretation.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Empty Document</para></term>
        <listitem><para>
          Both empty top level maps and no top level maps are now allowed, and
          hence so are empty documents.
        </para></listitem>
      </varlistentry>
    </variablelist>
  </chapter>

  <chapter>
    <title>Changes From The 22 Jul 2001 Draft</title>

    <para>
      Thanks to Joe Lapp for reviewing the 22 Jul 2001 draft and recommending
      these changes.
    </para>

    <variablelist>
      <varlistentry>
        <term><para>Phrasing fixes</para></term>
        <listitem><para>
          Fixed phrasing in the abstract, and sections 1.3, 2.1, 2.3.1, 2.4.3,
          2.4.4, 2.4.5, 2.4.6 and 2.5.3.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Production fixes</para></term>
        <listitem><para>
          Fixed productions: added production 47, 59, fixed productions 57, 58,
          60 and 64 (productions numbers in the 22 Jul 2001 draft are off by
          one in some cases). Most are bug fixes. Actual changes include
          allowing for empty lines surrounding a top level map, allowing an
          optional trailing separator line, and forbidding annotations which
          have no sensible semantics (anchor to null, anchor to a reference,
          shorthand for a reference).
        </para></listitem>
      </varlistentry>
    </variablelist>
  </chapter>

  <chapter>
    <title>Changes From The 23 Jun 2001 Draft</title>

    <variablelist>
      <varlistentry>
        <term><para>Merge Spec</para></term>
        <listitem><para>
          Due to the decision to leave all API related issues outside the core
          spec, the spec has been re-merged into a single file, covering just
          what used to be the introduction and serialization sections of the
          previous specs.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Character Encodings</para></term>
        <listitem><para>
          The spec now refers only to the Unicode standard. Due to the efforts
          by the Unicode and ISO/IEC 10646 groups, both standards are in almost
          complete agreement. The additional features provided by the ISO/IEC
          standard are rarely used in practice, while Unicode is simpler and is
          more widely supported by existing languages and systems.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Strict Indentation</para></term>
        <listitem><para>
          Indentation is now a strict 4 spaces per level. This allows for the
          new white space policy and the new block notation.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Shorthand Notation</para></term>
        <listitem><para>
          The spec introduces a shorthand notation for attaching special keys
          to any node kind (converting it to a map if necessary). This will
          need more work.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Null Nodes</para></term>
        <listitem><para>
          Null nodes have finally been added, after somehow eluding all
          previous versions.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Bullet Lists</para></term>
        <listitem><para>
          Change the <userinput>*</userinput> optional prefix for leaf list
          entries to a mandatory : and therefore remove the special name
          <quote>bulleted list entries</quote>.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Simplify Keys</para></term>
        <listitem><para>
          Multi-line simple keys are now out. The door is open for
          re-introducing them, however.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Change Whitespace Policy</para></term>
        <listitem><para>
          White space folding has been replaced by line break folding. White
          space is now always significant, except for indentation and for
          separation of structure tokens.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Block Scalar Syntax</para></term>
        <listitem><para>
          The syntax for block leaves has been replaced by a more elegant one.
        </para></listitem>
      </varlistentry>
    </variablelist>
  </chapter>

  <chapter>
    <title>Changes From The 16 Jun 2001 Draft</title>

    <variablelist>
      <varlistentry>
        <term><para>Split Spec</para></term>
        <listitem><para>
          The spec is now separated into several files. This allows different
          versions of the spec to share the same version of unchanged section,
          and make it easier to refer to a particular version of important
          pieces of the spec such as serialization and interfaces. All the HTML
          files use the same shared CSS file. Cross references between the
          separate parts of the spec are now relative, though references to
          older versions are absolute and refer to the main site.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Cyclical Graph</para></term>
        <listitem><para>
          Change the wording on the information model to allow for graphs with
          cycles. The alternative is to define the anchor semantics in such a
          way that would preclude cycles.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Null Character Escape</para></term>
        <listitem><para>
          The escape sequence \z was added to allow convenient escaping of the
          ASCII zero (null) character.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Remove Binary Scalars</para></term>
        <listitem><para>
          The information model now contains just one type of leaf. The special
          syntax for binary leaves has been removed. This functionality will be
          re-added in the form of a color.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Remove Class Shorthand</para></term>
        <listitem><para>
          The syntax no longer supports the !class syntax. This functionality
          will be re-added in the form of a color.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Bullet Lists</para></term>
        <listitem><para>
          Change the optional prefix for leaf list entries to
          <userinput>*</userinput> and rename such entries to <quote>bulleted
          list entries</quote>.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Make Keys More Scalars-Compatible</para></term>
        <listitem><para>
          Allow for multi-line simple keys and unify the description of leaf
          keys and values where it makes sense.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>HTML Tidying</para></term>
        <listitem><para>
          All the HTML pages have gone through Tidy. Also, all the HTML files
          have been run through an <ulink url="http://validator.w3.org/">HTML
          validation service</ulink> and a <ulink
          url="http://jigsaw.w3.org/css-validator/validator-uri.html">CSS
          validation service</ulink>. Broken links and spelling were checked
          using another <ulink
          url="http://www.zdnet.com/devhead/static/toolbox/">online HTML
          validator</ulink>. This needs to be repeated for all future drafts.
        </para></listitem>
      </varlistentry>
    </variablelist>
  </chapter>

  <chapter>
    <title>Changes From The 09 Jun 2001 Draft</title>

    <variablelist>
      <varlistentry>
        <term><para>Relationship with MIME</para></term>
        <listitem><para>
          Beyond using base64 for binary leaves, no additional special
          relationship with MIME is expected. Hence references to the MIME and
          mail RFCs were moved from section 1.1 (<quote>required
          reading</quote>) to section 1.2 (<quote>background material</quote>).
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Strict Indentation</para></term>
        <listitem><para>
          Indentation is now completely strict for all leaf styles. Also, the
          productions were changes to use a consistent semantics to the
          indentation level parameter.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>List Scalar Prefixes</para></term>
        <listitem><para>
          A list leaf entry may be prefixed by an optional : indicator to
          improve readability of multi-line simple leaf values.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Anchor Semantics</para></term>
        <listitem><para>
          Leading zeros are now ignored for comparing anchor strings.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>No Empty Line At Start</para></term>
        <listitem><para>
          The document production was fixed so as not to require an empty line
          at the start of a document.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Character Escapes</para></term>
        <listitem><para>
          The set of character escapes is now maximal (including the rare \e
          escape for the useful ASCII ESC character). Also, it is now possible
          to <quote>escape</quote> a line break in a quoted string (the
          previous drafts were inconsistent at this point).
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>32 Bit Characters</para></term>
        <listitem><para>
          The current draft allows such characters, and includes a specialized
          escaping format (<quote><userinput>\Uxxxxxxxx</userinput></quote>) to
          support them.
        </para></listitem>
      </varlistentry>
    </variablelist>
  </chapter>

  <chapter>
    <title>Changes From The 26 May 2001 Draft</title>

    <variablelist>
      <varlistentry>
        <term><para>Changes Section</para></term>
        <listitem><para>
          The changes section was added for easier comparison of different
          versions. The final draft will not contain this section.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Class Indicator</para></term>
        <listitem><para>
          The indicator was changed from <userinput>#</userinput> to
          <userinput>!</userinput> to allow for <userinput>#</userinput> to be
          used for comments.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>No Empty Line At End</para></term>
        <listitem><para>
          The document production was fixed so as not to require an empty line
          at the end of a document.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Strict Indentation</para></term>
        <listitem><para>
          Indentation in quoted strings and binary blocks is now strict to
          ensure readability.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Productions</para></term>
        <listitem><para>
          Problems in the productions were fixed, especially where related to
          white space issues and formatting of the result.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>BOM Comment</para></term>
        <listitem><para>
          The link to the Unicode FAQ was moved to section 2.2.2.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><para>Binary Scalars</para></term>
        <listitem><para>
          The information model now distinguishes between text and binary
          leaves.
        </para></listitem>
      </varlistentry>
    </variablelist>
  </chapter>
</book>
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