Wikilambda's first goal is to support the Wikimedia projects, but just as Wikidata it will support goals beyond that. This is a description of Wikilambda beyond Wikipedia.
Wikilambda is an open repository of code that anyone can use and contribute to.
Every page in Wikilambda represents a function. A function has a description, a list of parameters, test cases, a list of implementations in different programming languages, and further metadata. The implementations can be reused in other software projects (private apps or scripts), be called and executed online (either just in the browser or in a cloud environment or Jupyter or PAWS notebooks), composed to achieve more complex functionality, signed, analyzed or validated, and much more.
Wikilambda is a project in the spirit of Wikipedia, Wikidata, Wiktionary, and others, and it allows contributors from all over the world to create and maintain a library of functions, which can be used by anyone for any purpose. Every function can be supported by multiple implementations in different programming languages, test cases, pre- and postconditions, documentation, metadata in form of runtime estimates and complexity guarantees for the different implementations, etc. Users may call a function directly on the Website, or from their own code or applications, from a command line interface, or a local app. The function may be executed locally in the browser, in the cloud, or locally and embedded within the users application.
Wikilambda is intended to create both a well-defined common catalog of functions which can be widely reused, and also an environment where functions can be quickly combined and executed on the fly. Wikilambda aims to make life easier for developers, who can rely on this repository like on any external library, and for end users who can call functions as needed, in a way that is currently only available with a very uneven coverage through specific websites who are often written in the form of 1990s Websites with Java Applets.
All Functions are pure, in order to enable a secure sandboxed execution. Also, every implementation can be annotated with metadata and cryptographically signed. End users can select and audit which implementation of each function to use, depending on their available hardware resources and web of trust settings.
Wikilambda will allow easy access to large knowledge bases such as Wikidata, but also to binary input and output files. It is entirely possible to upload an image as an input file and return analysis results such as what is depicted on the image, or how many different colors the image has - or a different binary, e.g. in a different format. This will be made available to workflows on Commons.
Wikilambda continues the tradition of moving more computation, which has usually happened on the command line or with apps by more computer savvy computer users, to the Web and democratize access to functionality that was not available before. At the same time it will increase the productivity of developers everywhere as they can just use a large library of code instead of relying on properly copy and pasting answers from StackOverflow.
Unlike in Wikipedia, contributors will mostly create new implementations for a function instead of updating existing functions. The implementations can be automatically tested against the given tests, against each other, and further analyzed.
Implementations can be written in a number of different programming languages, and yet to be able to call functions implemented in other programming languages. The execution engine can smoothly (although not necessarily with the highest possible performance) operate in different languages. Although in most cases there is a large performance boost by composing functions within a single programming language, there is no requirement to do so. In many cases, the speed of development and the developers time will be more valuable than the additional computer cycles spent in the execution engine.