tooltip: Markdown
summary: A block of text formatted with Markdown directives.
description:
Markdown is a family of text-based formatting directives that can be used to
structure and format a block of text. A single markdown element in EML can contain multiple
formatting directives that support creation of sections and subsections with headings, a
wide variety of text formatting directives, the ability to include inline links to external
content, and the ability to embed inline citations, figures, and tables. EML's markdown element
follows the GitHub Flavored Markdown (GFM) extensions to the CommonMark specification. Clients that
display EML should use a markdown preprocessor to convert the Markdown formatting into an
appropriate display format such as HTML or PDF as appropriate. When a Markdown block is interleaved
with other blocks of text such as section and paragraph elements from Docbook, the Markdown section
should be interleaved as a block-level element in the flow of the document. This allows authors to
specify, for example, an initial section in DocBook, followed by a Markdown section, and then possibly
other sections in DocBook. This will likely be uncommon because Markdown and Docbook have similar
formatting capabilities, but it may be helpful when converting legacy documents that use DocBook.
Because markdown uses special characters that might be reserved by XML processors, one
must be careful to escape such characters, which is typically done by embedding the
text in a CDATA block, or other XML escaping measures. These escape sequences must be
unescaped before parsing the text with a Markdown processor.
Within a Markdown block, one can use embedded images to specify the location where an inline image
should be displayed within the document. For example, the syntax for an embedded image uses the
markdown reference syntax, for example ![Figure 1][fig.1.ab567w], where "fig.1.ab567w"
is the unique id attribute for the entity containing the reference to the image. When
client tools process such image links, they should inline the image data from that entity at the
location specified, which may involve, for example, resolving the image url from an
otherEntity section. This means that there is an implied link in all Markdown
documents of the form [id]: url/to/image "Optional title attribute", which is derived
from the metadata for each entity within a document. Users do not need to insert these links in
order to use them, but client software that might be generating HTML from the markdown will likely
need to generate them from the entity metadata if they are using an external Markdown pre-processor
to handle conversion to HTML and other languages.
Inline citations can also be used to cite scholarly works in the text of an EML
document. This follows the Pandoc syntax for citation keys, in which the citation keys
are in inside square brackets and separated by semicolons. Each citation is identified
by a key, which consists of an ‘@’ symbol and the citation identifier from the entry for
that citation. Citation keys may optionally have a prefix, a locator, and a suffix to
further qualify what is being cited. For example, a simple citation would be
constructed as '[@fegraus_2005]', and a list would be '[@jones_2001; @fegraus_2005]'.
The keys must be present in either the 'id' field of a
citation element in the EML document, or as the BibTex key in a 'bibtex' entry in the
EML document. It is a validation error to cite an entry for which the corresponding
citation key is not present in the EML document, and it is a validation error for the
same citation key to be reused across citation and bibtex elements in the document (each
citation identifier must be unique within the document). Clients that parse and display
EML documents should first gather up all citation and bibtex elements in the document to
create a citation database in bibtext format, and then pass that database along with the
text in markdown sections to pandoc or an equivalent tool to convert the citations into
properly formatted, human readable citations. Pandoc supports the use of Citation Style
Language (CSL) files to specify the formatting of citations upon conversion. See
http://citationstyles.org/ for more details.
Because bulleted lists and other structures within Markdown are dependent on indenting the raw
markdown text, authors and processors should pay close attention to formatting within the
markdown block. In particular, if the XML document within which the markdown block is embedded
is in an indented hierarchy, then the first non-whitespace character of the markdown block defines
the column for the leftmost column of the markdown, and all subsequent markdown should be indented
relative to that column. For example, if the first character of the markdown is in column 16
of the document, then all subsequent markdown lines in that block should also start on column 16.
A bulleted list would start on column 16, and its sublist would be indented four space to column 20. |
