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Co-authored-by: Thomas Tuegel <>

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The Kore Language

Kore is the "core" part of the K framework.

What is Kore all about?

In short, we need a formal semantics of K. In K, users can define formal syntax and semantics of programming languages as K definitions, and automatically obtain parsers, interpreters, compilers, and various verification tools for their languages. Therefore K is a language-independent framework.

Thanks to years of research in matching logic and reachability logic, we know that all K does can be nicely formalized as logic reasoning in matching logic. To give K a formal semantics, we only need to formally specify the underlying matching logic theories with which K does reasoning. In practice, these underlying theories are complex and often infinite, and it is tricky to specify infinite theories without a carefully designed formal specification language. And Kore is such a language.

Structure of this project

The /docs directory contains a comprehensive document Semantics of K that describes the mathematical foundation of Kore, and a BNF grammar that defines the syntax of Kore language.

The kore project is an implementation in Haskell of a Kore parser and symbolic execution engine, for use with the K Framework as a backend.


Besides git, you will need stack or cabal to build kore.

stack build kore
# or
cabal build kore

If using cabal, version 3.0 or later is recommended.


Developers will require all the dependencies listed above, in addition to the requirements and recommendations below.

Required dependencies

For integration testing, we require:

  • GNU make
  • The K Framework frontend, or curl to fetch an appropriate version. The frontend has other dependencies, most notably a Java runtime.

Recommended dependencies

For setting up a development environment, we recommend:

We recommend to keep ./ running in the background to keep important files (such as package descriptions) up-to-date, especially if the developer is using Cabal.

Running a language server

To run a language server, developers will need to activate the appropriate hie.yaml file:

ln -s hie-stack.yaml hie.yaml  # for Stack
# or
ln -s hie-cabal.yaml hie.yaml  # for Cabal
# or
ln -s hie-bios.yaml hie.yaml  # if all else fails

The project's dependencies must be installed before starting the language server:

stack build --test --bench --only-dependencies
# or
cabal build --enable-tests --enable-benchmarks --only-dependencies kore

Developing with Nix

We provide a shell.nix expression with a suitable development environment and a binary cache at The development environment is intended to be used with nix-shell and cabal.

When the .cabal package description file changes, run:

# Requires Nix to be installed.

This script is also run by an automatic workflow.