# Meta-Data

## Summary

The Meta-Data extension adds a syntax for defining meta-data about a document. It is inspired by and follows the syntax of MultiMarkdown. Currently, this extension does not use the meta-data in any way, but simply provides it as a `Meta` attribute of a Markdown instance for use by other extensions or directly by your python code.

This extension is included in the standard Markdown library.

## Syntax

Meta-data consists of a series of keywords and values defined at the beginning of a markdown document like this:

    Title:   My Document
    Summary: A brief description of my document.
    Authors: Waylan Limberg
             John Doe
    Date:    October 2, 2007
    blank-value:
    base_url: http://example.com

    This is the first paragraph of the document.

The keywords are case-insensitive and may consist of letters, numbers, underscores and dashes and must end with a colon. The values consist of anything following the colon on the line and may even be blank.

If a line is indented by 4 or more spaces, that line is assumed to be an additional line of the value for the previous keyword. A keyword may have as many lines as desired.

The first blank line ends all meta-data for the document. Therefore, the first line of a document must not be blank.

Alternatively, You may use YAML style deliminators to mark the start and/or end of your meta-data. When doing so, the first line of your document must be `---`. The meta-data ends at the first blank line or the first line containing an end deliminator (either `---` or `...`), whichever comes first. Even though YAML deliminators are supported, meta-data is not parsed as YAML.

All meta-data is stripped from the document prior to any further processing by Markdown.

## Usage

See Extensions for general extension usage. Use `meta` as the name of the extension.

## Accessing the Meta-Data

The meta-data is made available as a python Dict in the `Meta` attribute of an instance of the Markdown class. For example, using the above document:

    >>> md = markdown.Markdown(extensions = ['meta'])
    >>> html = md.convert(text)
    >>> # Meta-data has been stripped from output
    >>> print html
    <p>This is the first paragraph of the document.</p>

    >>> # View meta-data
    >>> print md.Meta
    {
    'title' : ['My Document'],
    'summary' : ['A brief description of my document.'],
    'authors' : ['Waylan Limberg', 'John Doe'],
    'date' : ['October 2, 2007'],
    'blank-value' : [''],
    'base_url' : ['http://example.com']
    }

Note that the keys are all lowercase and the values consist of a list of strings where each item is one line for that key. This way, one could preserve line breaks if desired. Or the items could be joined where appropriate. No assumptions are made regarding the data. It is simply passed as found to the `Meta` attribute.

Perhaps the meta-data could be passed into a template system, or used by various Markdown extensions. The possibilities are left to the imagination of the developer.

## Compatible Extensions

The following extensions are currently known to work with the Meta-Data extension. The keywords they are known to support are also listed.

- WikiLinks
  - `wiki_base_url`
  - `wiki_end_url`
  - `wiki_html_class`