Alloy Language & Analyzer

Designing flawless, efficient software

Alloy is a language and a toolkit for exploring the kinds of structures that arise in software design.

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Why use Alloy?

Fully Automated Analysis

Alloy comes with the Alloy Analyzer tool, which uses SAT-solving technology to find subtle flaws in software designs that you would never catch with testing. It is rapid, fully-automated analysis which gives results in highly customizable diagrams.

Declarative

Unlike a programming language, an Alloy model is declarative: it can describe the effect of a behaviour without giving its mechanism. This allows very succinct and partial models to be constructed and analyzed.

Easy Incrementality

In software engineering, one of the great benefits of Alloy is that you can analyze a tiny model. You can write three lines, and analyze it; add a few more lines, and analyze again. This incrementality makes Alloy especially good for exploring design ideas.

Frequently Asked

Questions

Unlike a programming language, an Alloy model is declarative: it can describe the effect of a behaviour without giving its mechanism. This allows very succinct and partial models to be constructed and analyzed. It is similar in spirit to the formal specification languages Z, VDM, Larch, B, OBJ, etc, but, unlike all of these, is amenable to fully automatic analysis in the style of a model checker.

Alloy has been used to model and analyze all kinds of system, but mostly with an emphasis on systems that involve complex structured state. Applications include: name servers, network configuration protocols, access control, telephony, scheduling, document structuring, key management, cryptography, instant messaging, railway switching, filesystem synchronization, semantic web. One area in which Alloy offers particular advantage over model checkers is for analyzing systems with configurations that are underdetermined, or that can change dynamically. For example, an analysis of the leader election phase of the Firewire prototol checked all behaviours involving all configurations of nodes (up to a certain size); a model checker would require that some configuration be hardwired.

In software engineering, one of the great benefits of Alloy is that you can analyze a tiny model. You can write three lines, and analyze it; add a few more lines, and analyze again. This incrementality makes Alloy especially good for exploring design ideas.

How to Get Started

Alloy Follow-Along Tutorial

Check out these tutorial slides and exercises by Rob Seater and Greg Dennis for an easy introduction to Alloy.

Tutorial found here

Software Abstractions

Read the book “Software Abstractions”, which introduces the Alloy as the language that captures the essence of software design simply and succinctly. Complete with lessons, exercises, and examples which are language-independent.

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More Resources

Find additional tutorials, grammar guides, reference materials, and helping learning resources to help guide you on your way to becoming an Alloy whiz.

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Get Involved

Alloy is truly a community effort, and we welcome contributions from all users, newcomers and seasoned professionals. All submitted works can be viewed in the ‘Resources’ section of the site. To submit your own work, email us at [email protected].

To get more of a flavor for Alloy, check out our latest works on the left.