TLA+

What TLA+ is

TLA+ is a free, open-source language and toolset for modeling software and hardware, especially concurrent and distributed systems. It helps teams express designs as specifications and check for fundamental errors before they become difficult or expensive to fix in code. PlusCal lets users describe algorithms and translate them into TLA+ models. TLC checks executable specifications for safety and liveness properties, while TLAPS mechanically checks TLA+ proofs.

The TLA+ Toolbox supports editing, PlusCal translation, TLC runs, error-trace exploration, and proof checking. A Visual Studio Code extension provides syntax highlighting, translation, parsing, TLC execution, result visualization, completion, and formatting for TLA+ and PlusCal. Command-line tools use tla2tools.jar and require Java 11 or later. The tools and Toolbox repository are licensed under the MIT License. The Eclipse-based Toolbox GUI is currently unmaintained, has minor unfixed bugs, and has help pages as its only user manual. The listed platforms are extension, Linux, macOS, and Windows.

Who it suits

TLA+ suits software and hardware designers modeling concurrent or distributed systems. It is relevant to teams that want to check specifications with TLC or mechanically check proofs with TLAPS.

Limits

The TLA+ tools are free. Command-line tools require Java 11 or later; the Toolbox GUI is currently unmaintained and has minor unfixed bugs.

Getting started

1. Visit the TLA+ website.
2. Choose the TLA+ Toolbox, Visual Studio Code extension, or command-line tools.
3. For command-line use, obtain tla2tools.jar and use Java 11 or later.
4. Write a TLA+ specification or describe an algorithm in PlusCal.
5. Run TLC to check an executable specification, or use TLAPS to check a proof.

Verdict

TLA+ provides model checking, proof checking, and editor options for system design verification. The Toolbox is an available interface, but its stated maintenance and documentation limitations are worth considering.