Runtime provenance refinement for notebooks

Computational notebooks (e.g., Jupyter or Apache Zeppelin) have become a popular choice for data exploration, preparation, and ETL. Notebooks are more suited for interactive development of data pipelines than classical workflow systems, because they provide immediate feedback for the results of a computation and do not require the full computation to be specified upfront. However, the notebook model suffers from poor reproducibility, does not support automatic incremental re-evaluation of code when the code or inputs change, and does not allow for parallel execution of cells --- all symptoms of its kernel-based evaluation strategy. We propose a new "workbook" model that combines the usability of notebooks with the provenance and parallel execution capabilities of workflow systems. This is made possible through a novel approach that refines a static approximation of provenance for Python code at runtime and a scheduler that dynamically adapts the execution order of cells based on data dependencies detected or refuted at runtime. We demonstrate the feasibility of this approach using a prototype implementation in our notebook engine Vizier.