Acre, an open source platform for building Freebase apps

Freebase is an open, Creative Commons licensed repository of structured data that contains information about 12 million real-world entities including people, places, films, books, events, businesses, and almost any other thing you can imagine. Our graph database has about 400 million facts and connections between entities, and all of it is accessible via our REST API. Freebase was acquired by Google last month, and one thing we knew would happen was that Freebase would become “even more open.”

We first launched Acre, the hosted, server-side JavaScript platform behind Freebase Apps, just over a year ago. Since then it's become more and more important to us and to the Freebase community. Not only are all kinds of individual developers and businesses using Acre to build apps and integrate Freebase data into their own platforms, but we've also recently announced our intention to develop the Freebase.com site on the platform, too.

Until now, Acre development has always been tied to Freebase.com, meaning that you need to develop your Acre apps on our server, using our app editor. But we know that most software developers prefer to use their own native development environments -- their favourite text editor, version control system, and so on -- so lately we've been working on ways to make Acre work with source code that's not stored in Freebase.

Last week we announced that we're releasing the Acre platform as open source software. This means that you can run Acre on your own machine, pulling templates and other files from your local disk and using your own development environment. While Acre still has close ties to Freebase (such as API hooks for easily making Freebase queries), this also means that you'll be able to develop standalone, non-Freebase apps using the platform if you want. And, by running Acre on your own platform, you can avoid the resource limitations that are necessary in a shared environment.

If you're interested in server-side JavaScript platforms, you may also be interested in some of the technical details of Acre.

• Acre is based on Rhino, Mozilla's implementation of Javascript in Java. (In fact, "Acre" stands for "A Crash of Rhinos Evaluating.") Acre, by default, uses the Jetty servlet engine as its HTTP server, but can be run in any servlet container.
• Acre includes a module system that supports high-latency source retrieval using extensive caching. Although Acre was originally designed to fetch data only from Freebase itself, it can also fetch data from disk and will support a wider range of require() options such as WebDAV.
• Acre is capable of running on Google AppEngine, with support for the Keystore and for synchronous and asynchronous HTTP requests. Soon, Freebase's own Acre installation will run on AppEngine.

Please download Acre and try it out, and let us know what you think! You might also like to look at some of our other open source releases, like freebase-python (a Python library for working with the Freebase API) or freebase-suggest (a jQuery plugin that makes it easy to have your users select Freebase topics based on any criteria). For more information about Freebase and our open source efforts, see the Freebase wiki or post to the freebase-discuss mailing list.

By Kirrily Robert, Freebase Team