Summary
-------

Enhance the `javadoc` tool to generate [HTML5][h5] markup.


Goals
-----

Provide an option to the standard doclet to request either HTML 4 or HTML5 output.
The HTML5 markup is semantic, i.e., clearly separating meaning from
style and content. The parts of the pages generated by the standard doclet
using HTML5 markup satisfy accessibility requirements.


Non-Goals
---------

It is a not a goal to replace the current three-frame/no-frame structure of the
generated HTML pages; that may be the subject of a future JEP.

It is not a goal to mandate the use of HTML5 in documentation comments,
nor is it a goal to provide the ability to convert documentation comments written using 
HTML 4 to HTML5.


Motivation
----------

In JDK 8 and older releases, the standard doclet generated pages in [HTML 4.01][h401], 
which is an old standard, and not not provide support for satisfying accessibility requirements.  
[HTML5][h5] is the latest standard for HTML.  HTML5 increases the semantic value of web 
pages and makes it easier to create accessible web pages.


Description
-----------

  - A command-line option is added to the standard doclet to request a
    specific type of output markup.  HTML4, which is the current type,
    will be the default.  HTML5 will become the default in JDK 10.

  - The semantic value of the generated HTML is improved by using
    structural HTML5 elements such as `header`, `footer`, `nav`, _etc._

  - The HTML5 markup implements the [WAI-ARIA standard][wai] for
    accessibility.  Specific roles are assigned to elements in the
    HTML document using the role attribute.

  - The `-Xdoclint` feature is update to check documentation comments
    for common errors, based upon the requested type of output markup.


Testing
-------

Tests are provided to ensure that:

  - The HTML5 markup is valid
  - The HTML5 markup is accessible
  - The new command-line option works correctly
  - The HTML5 markup works across all supported browsers

The lack of automated tools to test accessibility hampers
comprehensive accessibility testing. A representative sample
of different types of pages can checked using online web-based
tools.


[h401]: http://www.w3.org/TR/html401/
[h5]: https://www.w3.org/TR/html5/
[wai]: http://www.w3.org/WAI/intro/aria