In essence, the package allows to write functional code directly in Python: statements merely specify relationships among variables through operations. Evaluation of any variable given the values of other variables is then de facto:

• lazy: only operations participating in the determination of the requested value are executed,
• concurrent: operations can be executed by a thread pool of arbitrary size.

In addition, relationships among variables can be traversed in both directions, allowing a form of backpropagation of information through the computation network that would be cumbersome to implement in an imperative manner.