What is it?
vfmd is a variant of John Gruber's Markdown with an unambiguous specification of its syntax.
It's just plain-vanilla Markdown, but formalized with a spec. Hence vfmd, or vanilla-flavoured markdown. (There are some differences with the original Markdown, but nothing big.)
For a more detailed introduction, see Introducing vfmd.
Why a spec?
Because the myriad implementations of Markdown don't quite agree on how certain Markdown texts should be handled, which means that we never are sure where our Markdown is going to work, and where not. For example, in an ideal world, the Markdown we write using an app on my tablet should work perfectly with a blogging engine, even though they use different implementations of Markdown, created for different purposes and for different platforms. An important reason why that's not the case now is because Markdown has no spec - what exists, for the original Markdown, and for the other variants, is a syntax guide that tells us how to write in Markdown, not a spec that tells us unambiguously how Markdown should be interpreted.
For more details on the motivation behind vfmd, see Introducing vfmd.
Does it have features 'foo' and 'bar'?
vfmd supports all syntax constructs in John Gruber's Markdown, with some differences. It does not define the syntax for the additional features available in some variants of Markdown, like tables, definition lists or footnotes. However, extendability is part of the vfmd design, so the specification includes information on how the syntax can be extended to support features like that in an implementation of vfmd.
The vfmd project aims to deliver the following:
Specification: A document describing the syntax for Markdown unambiguously and intended for use in designing parsers for Markdown. The specification document can be found here.
Syntax guide: A document describing the syntax for Markdown, intended for use by document authors. This document needs to be consistent with the specification, and can have some ambiguities. The syntax guide can be found here.
Tests: A test suite to verify that an implementation confirms to the specification for HTML output. This should cover all corner cases and needs to be consistent with the specification. The current set of testcases can be found here.
Status: In progress; almost done.
Implementation: An implementation of the specification for converting vfmd text to HTML. The implementation will be extendable to support additional syntax elements in the way described in the specification. A working implementation written in C++ is here.
How can you help?
Please take a look at the specification and the syntax guide, and try out the implementation. If you find any errors, ambiguities or inconsistencies, please submit an issue or pull-request in the appropriate repository in GitHub.
If you have comments on the strategy or the core idea, please contact me.