Ott

Ott is a tool for writing definitions of programming languages and calculi. It takes as input a definition of a language syntax and semantics, in a concise and readable ASCII notation that is close to what one would write in informal mathematics. With appropriate annotations, it can then generate output:

• a LaTeX source file that defines commands to build a typeset version of the definition;
• a Coq version of the definition;
• a HOL version of the definition;
• an Isabelle/HOL version of the definition;
• a Lem version of the definition;
• an OCaml version of the syntax of the definition; and
• (experimental) a menhir parser and crude pretty printer for the syntax.

Additionally, it can be run as a filter, taking a LaTeX/Coq/Isabelle/HOL/Lem/OCaml source file with embedded (symbolic) terms of the defined language, parsing them and replacing them by typeset terms.

Most simply, Ott can be used to aid informal LaTeX mathematics. Here it permits the definition, and terms within proofs and exposition, to be written in a clear, editable, ASCII notation, without LaTeX noise. It generates good-quality typeset output. By parsing (and so sort-checking) this input, it quickly catches a range of simple errors, e.g. inconsistent use of judgement forms or metavariable naming conventions.

That same input can be used to generate formal definitions, for Coq, HOL, Isabelle, and Lem. It should thereby enable a smooth transition between use of informal and formal mathematics. Additionally, the tool can automatically generate definitions of functions for free variables, single and multiple substitutions, subgrammar checks (e.g. for value subgrammars), and binding auxiliary functions. At present only a fully concrete representation of binding, without quotienting by alpha equivalence, is fully supported. An experimental backend generates a locally-nameless representation of terms for a subset of the Ott metalanguage: details can be found at http://moscova.inria.fr/~zappa/projects/ln_ott.

The distribution includes several examples, in varying levels of completeness: untyped and simply typed lambda-calculus, a calculus with ML polymorphism, the POPLmark Fsub with and without records, an ML module system taken from (Leroy, JFP 1996) and equipped with an operational semantics, and LJ, a lightweight Java fragment. More substantially, Ott has been used for work on iJAM and LJAM, Java Module Systems, by Rok Strnisa, and semantics for OCaml light, by Scott Owens.

As of 2020, Ott remains in continuous use.

Documentation

• the manual is in the Ott github built_doc directory, or here (html)

• Binding and Substitution. Susmit Sarkar, Peter Sewell, Francesco Zappa Nardelli. Note, 2007.

• The experimental Coq locally-nameless backend (html). Francesco Zappa Nardelli. Note, 2009.

Papers

• Ott: Effective Tool Support for the Working Semanticist. Peter Sewell, Francesco Zappa Nardelli, Scott Owens, Gilles Peskine, Thomas Ridge, Susmit Sarkar, Rok Strnisa. Journal of Functional Programming 20(1):71-122, 2010

• Ott: Effective Tool Support for the Working Semanticist. Peter Sewell, Francesco Zappa Nardelli, Scott Owens, Gilles Peskine, Thomas Ridge, Susmit Sarkar, Rok Strnisa. In ICFP 2007

• Ott or Nott. Stephanie Weirich, Scott Owens, Peter Sewell, Francesco Zappa Nardelli. In WMM 2010: 5th ACM SIGPLAN Workshop on Mechanizing Metatheory.

People

Ott has been principally developed by Peter Sewell, Francesco Zappa Nardelli, and Scott Owens, with contributions from many others including Joey Eremondi, Hannes Mehnert, Karl Palmskog, Matthew Parkinson, Thibaut Perami, Gilles Peskine, Alastair Reid, Tom Ridge, Susmit Sarkar, Rok Strnisa, Viktor Vafeiadis.

To install and build

Ott is available as an opam package and a github repo.

With OPAM (released version)

First, ensure you have opam (the OCaml package manager) installed, version 2.0 or greater (opam 1 versions of ott are no longer supported). You can use your system's package manager e.g. sudo apt-get install opam (e.g. on Ubuntu 20.04) or follow the instructions from the opam website. On older Ubuntu versions you will not be able to use their package manager's opam 1 version, and will need to install opam 2 following the instructions on the opam website.

Then opam install ott will install the latest Ott version. The Emacs mode will be in $(opam config var prefix)/share/emacs/site-lisp, and documentation in $(opam config var prefix)/doc/ott.

If you want to use Ott with the Coq proof assistant, to install the Ott auxiliary files for Coq, first activate the coq-released OPAM repository:

opam repo add coq-released https://coq.inria.fr/opam/released

and then run opam install coq-ott.

With OPAM (github checkout)

In the checkout directory, run opam pin add ott ..

To rebuild and reinstall after local changes, run opam upgrade --working-dir ott (or opam upgrade -w ott).

Without OPAM

Ott depends on OCaml version 4.07.0 or later and the ocamlgraph package. It builds with (at least) OCaml 4.07.0 and 4.14.0, and ocamlgraph 1.8.8.

The command make (make world) builds the ott binary in the bin/ subdirectory.

This will compile Ott using ocamlopt. To force it to compile with ocamlc (which may give significantly slower execution of Ott), do make world.byt.

To build the Ott auxiliary files for Coq, go to the coq/ subdirectory and run make. To install the resulting files in Coq's user-contrib, run make install.

To run

Ott runs as a command-line tool. Executing ott shows the usage and options. To run Ott on the test file tests/test10.ott, generating LaTeX in test10.tex and Coq in test10.v, type:

ott -i tests/test10.ott -o test10.tex -o test10.v

Isabelle, HOL, and Lem can be generated with options -o test10.thy, -o test10Script.sml, and -o test10.lem, respectively.

The Makefile has various sample targets, make tests/test10.out, make test7, etc. Typically they generate:

from files test10.ott, test8.ott, etc., in tests/.

Editor Plugins

Emacs mode

The file emacs/ott-mode.el defines a very simple Emacs mode for syntax highlighting of Ott source files. It can be used by, for example, adding the following to your .emacs file, replacing PATH by a path to your Ott Emacs directory.

(setq load-path (cons (expand-file-name "PATH") load-path))
(require 'ott-mode)

For installations using OPAM on *nix systems, it is sufficient to use the following code, which will call opam config var prefix at load-time.

(setq opam-share (substring (shell-command-to-string "opam config var share") 0 -1))
(add-to-list 'load-path (concat opam-share "/emacs/site-lisp"))
(require 'ott-mode)

Visual Studio Code

There is a plugin for VSCode, which features syntax highlighting and inline error reporting.

Mailing lists

• cl-ott-announce announcement mailing list
• cl-ott-discuss discussion mailing list

Bug Tracker

• Please now use the github issue tracker (though our resources for fixing issues are very limited)
• The previous issue tracker is here

Directory contents

Examples

The following LaTeX, Coq, HOL, and Isabelle files, except the proof scripts, are all automatically generated from the Ott sources.

(*) These systems would need explicit alpha conversion in the rules to capture the intended semantics using the fully concrete representation.

Copyright information

The ocamlgraph library is distributed under the LGPL (from http://www.lri.fr/~filliatr/ftp/ocamlgraph/); we include a snapshot for convenience. For its authorship and copyright information see the files therein.

All other files are distributed under the BSD-style licence in LICENCE.