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<h2 align=center>Specification for the META.yml file</h2>

This document describes version 1.0 of the META.yml specification.

The META.yml file describes important properties of contributed Perl
distributions such as the ones found on <a
href="http://www.cpan.org">CPAN</a>. It is typically created by tools
like <a
href="http://search.cpan.org/author/KWILLIAMS/Module-Build/">Module::Build</a>
and <a
href="http://search.cpan.org/author/MSCHWERN/ExtUtils-MakeMaker/">ExtUtils::MakeMaker</a>.

The fields in the META.yml file are meant to be helpful to people
maintaining module collections (like CPAN), for people writing
installation tools (like <a
href="http://search.cpan.org/author/ANDK/CPAN/">CPAN.pm</a> or <a
href="http://search.cpan.org/author/KANE/CPANPLUS/">CPANPLUS</a>), or
just people who want to know some stuff about a distribution before
downloading it and starting to install it.

<h3>Format</h3>

META.yml files are written in the <a
href="http://www.yaml.org/">YAML</a> format. The reasons we chose
YAML instead of, say, XML or Data::Dumper are discussed in <a
href="http://archive.develooper.com/makemaker@perl.org/msg00405.html">this
thread</a> on the MakeMaker mailing list.

The first line of a META.yml file should be a valid <a
href="http://www.yaml.org/spec/#.Document">YAML document header</a>
like <tt>"--- #YAML:1.0"</tt>.

<h3>Fields</h3>

The rest of the META.yml file is one big YAML <a
href="http://www.yaml.org/spec/#.-syntax-mapping-Mapping-">mapping</a>,
whose keys are described here.

<ul>

<li>name 
Example: Module-Build

The name of the distribution. Often created by taking the "main
module" in the distribution and changing "::" to "-". Sometimes it's
completely different, however, as in the case of the <a
href="http://search.cpan.org/author/GAAS/libwww-perl/">libwww-perl</a>
distribution.

<li>version 
Example: 0.16

The version of the distribution to which the META.yml file refers.
This is a mandatory field.

The version is essentially an arbitrary string, but must be
 only ASCII characters, and strongly should be of the format
 integer-dot-digit-digit, i.e. <tt>25.57</tt>, optionally followed by
 underscore-digit-digit, i.e. <tt>25.57_04</tt>.

The standard tools that deal with module distribution (PAUSE, CPAN,
 etc.) form an identifier for each distribution by joining the 'name'
 and 'version' attributes with a dash (<tt>-</tt>) character. Tools
 who are prepared to deal with distributions that have no version
 numbers generally omit the dash as well.

<li>license 
Example: perl

a descriptive term for the licenses ... not authoritative, but must
 be consistent with licensure statements in the READMEs, documentation, etc.

The license under which this distribution may be used and
redistributed. See <a
href="http://search.cpan.org/author/KWILLIAMS/Module-Build/">Module::Build</a>
for the list of valid options.

<li>license_uri 

 This should contain a URI where the exact terms of the license may be found.

(change "unrestricted" to "redistributable"?)

<li>distribution_type 
Example: module

What kind of stuff is contained in this distribution. Most things on
CPAN are <code>module</code>s (which can also mean a collection of
modules), but some things are <code>script</code>s.

This field is basically meaningless, and tools (like Module::Build or
MakeMaker) will likely stop generating it in the future.

<li>private 
WTF is going on here?

index_ignore: any application that indexes the contents of
distributions (PAUSE, search.cpan.org) ought to ignore the items
(packages, files, directories, namespace hierarchies).

<li>requires 
Example: 

&nbsp;&nbsp;Data::Dumper: 0 
&nbsp;&nbsp;File::Find: 1.03 
 

A YAML <a
href="http://www.yaml.org/spec/#.-syntax-mapping-Mapping-">mapping</a>
indicating the Perl modules this distribution requires for proper
operation. The keys are the module names, and the values are version
specifications as described in the <a
href="http://search.cpan.org/author/KWILLIAMS/Module-Build/lib/Module/Build.pm">
documentation for Module::Build's "requires" parameter</a>.

Note: the exact nature of the fancy specifications like
<tt>"&gt;= 1.2, != 1.5, &lt 2.0"</tt> is subject to
change. Advance notice will be given here. The simple specifications
like <tt>"1.2"</tt> will not change in format.

<li>recommends 
Example: 

&nbsp;&nbsp;Data::Dumper: 0 
&nbsp;&nbsp;File::Find: 1.03 
 

A YAML <a
href="http://www.yaml.org/spec/#.-syntax-mapping-Mapping-">mapping</a>
indicating the Perl modules this distribution recommends for enhanced
operation.

<li>build_requires 
Example: 

&nbsp;&nbsp;Data::Dumper: 0 
&nbsp;&nbsp;File::Find: 1.03 
 

A YAML <a
href="http://www.yaml.org/spec/#.-syntax-mapping-Mapping-">mapping</a>
indicating the Perl modules required for building and/or testing of
this distribution. These dependencies are not required after the
module is installed.

<li>conflicts 
Example: 

&nbsp;&nbsp;Data::Dumper: 0 
&nbsp;&nbsp;File::Find: 1.03 
 

A YAML <a
href="http://www.yaml.org/spec/#.-syntax-mapping-Mapping-">mapping</a>
indicating the Perl modules that cannot be installed while this
distribution is installed. This is a pretty uncommon situation.

- possibly separate out test-time prereqs, complications include: can
tests be meaningfully preserved for later running?  are test-time
prereqs in addition to build-time, or exclusive?

- make official location for installed *distributions*, which can
contain tests, etc.

<li>dynamic_config 
Example: 0

A boolean flag indicating whether a <tt>Build.PL</tt> or
<tt>Makefile.PL</tt> (or similar) must be executed, or whether this
module can be built, tested and installed solely from consulting its
metadata file. The main reason to set this to a true value if that
your module performs some dynamic configuration (asking questions,
sensing the environment, etc.) as part of its build/install process.

Currently <tt>Module::Build</tt> doesn't actually do anything with
this flag - it's probably going to be up to higher-level tools like
<tt>CPAN.pm</tt> to do something useful with it. It can potentially
bring lots of security, packaging, and convenience improvements.

<li>generated_by 
Example: Module::Build version 0.16

Indicates the tool that was used to create this META.yml file. It's
good form to include both the name of the tool and its version, but
this field is essentially opaque, at least for the moment.

* Ingy's suggestions
short_description: (add as field, containing abstract, maximum 80 characters, suggested minimum 40 characters)
description: (long version of abstract, should add?)
maturity: alpha, beta, gamma, mature, stable
author_id, owner_id: 
categorization, keyword, chapter_id: 
URL for further information: (could default to search.cpan.org on PAUSE)

namespaces: can be specified for single elements by prepending
dotted-form, i.e. "com.example.my_application.my_property".  Default
namespace for META.yml is probably "org.cpan.meta_author" or
something.  Precedent for this is Apple's Carbon namespaces, I think.

</ul>

<h3>History</h3>

<ul>
<li>March 14, 2003 (Pi day) - created version 1.0 of this document.</li>
<li>May 8, 2003 - added the "dynamic_config" field, which was
 missing from the initial version.</li> 
</ul>

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