Hets (The heterogeneous tool set)

Hets is a parsing, static analysis and proof management tool incorporating various provers and different specification languages, thus providing a tool for heterogeneous specifications. Logic translations are first-class citizens.

Supported languages

The following provers have been connected to Hets:

The structuring constructs of the heterogeneous specification language are those of the language CASL, plus some constructs to select languages (logics) and language translations. The heterogeneous specification language of Hets is called HetCASL. However, Hets can also read other structuring constructs, like those of Haskell, Maude or OWL. All these are mapped to so-called development graphs and processed with a proof calculus for heterogeneous development graphs that allows to decompose global proof obligations into local ones (during this, Hets also needs to compute colimits of theories over the involved logics).

Hets is based on a graph of logics and logic translations. The overall architecture is depicted below. Adding new logics and logic translations to Hets can be done with moderate effort by adding some Haskell code to the Hets source. With the Latin project, this becomes much easier: logics (and in the near future also logic translations) can be declaratively specified in LF.

Architecture of the heterogeneous tool set Hets

Using Hets

You can try out Hets using the Web-based interface

The best way to use hets is under Ubuntu. Possibly run this OS in a virtual box.

A compressed (1.2G, uncompressed 4.2G) virtual box image can be downloaded from here. username/password is ubuntu/reverse.

Installing Hets under Ubuntu

The basic system

sudo apt-get install software-properties-common
sudo apt-add-repository ppa:hets/hets
sudo apt-get update
sudo apt-get install hets-desktop

Hets development

For Hets development additionally type in

sudo apt-add-repository -s "deb http://ppa.launchpad.net/hets/hets/ubuntu xenial main"
sudo apt-get update
sudo apt-get build-dep hets-desktop

Replace 'xenial' with the Ubuntu version that you use. The Hets sources should be obtained from the git repository (see the end of this page).

Installing Hets under Archlinux

We provide the AUR-packages hets-desktop-bin and hets-server-bin to install 64 bit binaries of Hets/Hets-server. If you would like to compile Hets yourself, you can install one of the AUR-packages hets-desktop and hets-server.

Installing Hets under OS X/macOS (10.9 (Mavericks) and greater)

Hets binaries

(these are usually not needed but may replace the binaries from above)

How to use a hets binary?

Just download the binary and put it somewhere in the $PATH.

Download the CASL libraries and set $HETS_LIB to the folder containing these.


Hets is called with

hets filename


hets -g filename

For entering the command line mode, just call

hets -I

For a short description of the options, call

hets --help

Restful Interface

See RESTful Interface

User Documentation

A good starting point is the Hets user guide and the Hets user guide for Common Logic users. Furthermore two vidoes showing a heterogeneous proof are available:

For a formal introduction to hets see the introductory paper The Heterogeneous Tool Set by Till Mossakowski, Christian Maeder, Klaus Lüttich and Stefan Wölfl. For more in-depth information about Hets see the thesis Heterogeneous specification and the heterogeneous tool set by Till Mossakowski.

For questions related to hets there is a mailing list.

Emacs Mode for CASL specifications

To support writing CASL specifications we have an emacs mode

Including specifications in LaTeX documents

With the option "-o pp.tex" hets can produce nice LaTeX output from your specifictions that can be embedded in your publications using the hetcasl.sty style file.


A good starting point is the code documentation for Hets - the Heterogeneous Tool Set.

Since Hets is rather large and complex we recommend following the interactive session in Debugging and Testing Hets to get familiar with the central datastructures of Hets.

The formal background and the general structure of Hets is described in chapter 7 of Heterogeneous specification and the heterogeneous tool set.


Hets is written in Haskell, and is compiled using GHC using a couple of language extensions. Among the Haskell books and tutorials we recommend Real World Haskell. The language definition covers the Haskell98 standard which we are supposed to stick to in most cases. Make sure that you are familiar with at least the most common library functions of the Prelude. For searching or looking up any library functions you may also try Hoogle.

Also look into programming guidelines and things to avoid in Haskell.


Dependencies can be installed as specified in Hets Development

Contributing changes

Before committing haskell source files you may check compliance to the programming guidelines:

Also have a look at the current Release Notes, Debugging and Testing Hets,Code Review and Branching.

If you want to participate in the Hets development feel free to tell us via our mailing list for Hets developers. This mailing list can also be read via http://news.gmane.org/gmane.comp.lang.hets.devel.

If you wish to make larger changes we generally recommend forking this repository. You can however request access to this repository if you plan on contributing regularly.

Build Hets using Stack

Troubleshooting & Useful Tools

Hints for contributors switching from svn to git


The Hets source code is licensed under the GPLv2 or higher