Forest

Forest (forestdb.org) is a community repository for
generative models written in probabilistic programming languages, mainly
Church and
WebPPL. Most code boxes are editable and
run directly in the browser. Forest is maintained as a teaching resource and
archive; it has long served as the home for class projects from courses such
as Probabilistic Languages Understanding.

Adding models

To add a new model, create a markdown file in the
models directory.
You can do this directly on GitHub: add model.

For an example of the file format, see
example.md.
A minimal model file looks like this:

---
layout: model
title: My Model
model-language: webppl
model-status: code
model-category: Probabilistic Language Understanding
model-tags: concepts, program induction
---

Prose describing the model.

~~~~
flip(0.5)
~~~~

Frontmatter fields:

model-language (required to make code boxes runnable): webppl or church.
model-language-version (optional, webppl only): pins a webppl version.
Available: pre-v0.7, v0.9.6, v0.9.7, v0.9.9, v0.9.13, v0.9.15
(default).
model-status (optional): code (code runs), static (code shown as a
non-runnable listing; add a model-status-verbose explanation), link
(page links to external code), or hidden (not listed on the front page).
model-category (optional but encouraged): one of
Concept Learning, Reasoning about Reasoning,
Probabilistic Language Understanding, Counterfactuals and Explanations,
Machine Learning, Nonparametric Models, Bayesian Data Analysis,
Undirected Constraints, Inverse Dynamics, PPAML Challenge Problems,
Miscellaneous. Models without a category are listed under "Uncategorized"
on the front page.
model-tags (optional): arbitrary comma-separated words or phrases.

To display a code box without making it runnable (e.g. to show a model
fragment), mark the fence with norun:

~~~~ norun
// this box renders as static code
~~~~

Machine-readable index

forestdb.org/models.json lists every model
with title, URL, markdown source URL, language, version, status, category, and
tags.

Local development

The site is plain Jekyll, built by GitHub Pages from
the gh-pages branch. To preview locally:

docker run --rm -v "$PWD":/site -p 4000:4000 -w /site jekyll/jekyll \
  jekyll serve --host 0.0.0.0

then open localhost:4000.

All JavaScript and CSS (jQuery, Bootstrap, the webppl runtimes, webchurch) is
vendored under assets/, so the site has no runtime dependencies on external
CDNs. To support a new webppl version, build or download the browser bundle,
add it as assets/webppl/webppl-<version>.js, and add the version to the list
in this README and to scripts/test-models/package.json.

Continuous checks

Two scheduled GitHub Actions keep the site healthy (see .github/workflows/):

Test models runs every webppl model headless against its declared
webppl version (scripts/test-models/runner.js) and files a report issue.
Run locally with cd scripts/test-models && npm install --install-strategy=nested && node runner.js
(nested install needed for webppl 0.6.1's hardcoded module paths).
Check links runs lychee over all model pages and files a report issue
when links break.