Feedmark
========

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Copyright (c) 2019-2024 Chris Pressey, Cat's Eye Technologies
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*Version 0.17.  Subject to change in backwards-incompatible ways without notice.*

**Feedmark** is a format for embedding structured data in Markdown files
in a way which is both human-readable and machine-extractable.
The structured data is intended to be "curational" in nature.
Articles in [Chrysoberyl][], [Some Games of Note][], and other collections
of Cat's Eye Technologies' are written in Feedmark.

Informally, the format says that every `h3`-level heading in the
Markdown file gives the title of an entity, and may be followed
immediately by the entity's "plaque", which is a bullet list
where every item is in the form "field-name: field-value".

Why Feedmark?
-------------

In the same way that a Markdown file is still a readable text file,
which is nice, a Feedmark file is still a readable Markdown file,
which is still a readable text file, which is nice.

While some structured data formats like YAML are fairly easy to
read, many web-based file viewers (such as GitHub, GitLab, Forgejo,
klaus, etc.) will automatically format Markdown as HTML, making it
that much nicer.

Example Feedmark documents can be found in the `eg/` directory,
and in the projects mentioned above.

Implementation
--------------

This repository contains a Python 3 program, `feedmark`, which is a
reference implementation of a processor for the Feedmark format.

To use it, you can clone this repository and run it as `bin/feedmark`
from the directory of your clone, or you can put the `bin` directory
on your executable search path, and run it as `feedmark` anywhere.

Or you can install it using `pip`:

    pip install Feedmark==0.17

(Depending on your needs, you may wish to establish a virtual environment
first.  How to do this is outside the scope of this document.)

`feedmark` is currently able to do the following things:

### Parse and check Feedmark documents

Loading documents will always check that they are minimally well-formed.

    feedmark eg/*.md

You can also check documents against a Feedmark schema, which is
simply another Feedmark document, one in which each entry describes
a property that entries should have.

    feedmark eg/*Sightings*.md --check-against=eg/schema/Llama\ sighting.md

### Convert Feedmark documents to various formats

The original use case of this tool was to generate an Atom (née RSS)
feed of entries in a document:

    feedmark "eg/Recent Llama Sightings.md" --output-atom=feed.xml
    python3 -m http.server 7000 &
    python3 -m webbrowser http://localhost:7000/feed.xml

It can now also output entries as JSON, indexed by entry, or by
property, or by publication date:

    feedmark --output-json eg/*.md
    feedmark --by-property eg/*.md
    feedmark --by-publication-date eg/*.md

...or as Markdown or HTML (using the `toc` extension, which generates
link anchors on headings compatible with the ones generated by GitHub
and which are now in widespread use).

    feedmark --output-markdown eg/*.md
    feedmark --output-html eg/*.md

### Rewrite documents in-place

Feedmark documents can be rewritten in-place; they will be parsed as Feedmark,
and then written out as Markdown, to the same filename that were read in as
input.  **Note!**  This is a destructive operation, and it isrecommended that
the files being processed this way are kept under version control such
as `git`, as this will easily allow the changes to be reverted if necessary.

    feedmark --rewrite-markdown eg/*.md

### Interlink documents

Markdown supports "reference-style" links, which are not inline
with the text.

`feedmark` can rewrite reference-style links that match the name of
an entry in a previously-created "refdex", so that they
can be kept current and point to the canonical document in which the
entry exists, since it may exist in multiple, or be moved over time.

    feedmark eg/*.md --output-refdex >refdex.json
    feedmark --input-refdex=refdex.json --rewrite-markdown eg/*.md

See also
--------

Feedmark is a subset of Markdown, which is something it has in common
with [Falderal][], however it has decidedly different goals.

See [TODO.md](TODO.md) for planned features and [HISTORY.md](HISTORY.md)
for a record of features added in past versions.

[Falderal]: https://catseye.tc/node/Falderal
[Chrysoberyl]: https://git.catseye.tc/Chrysoberyl/
[Some Games of Note]: https://catseye.tc/node/Some%20Games%20of%20Note