The document discusses using machine learning techniques on provenance metadata to optimize repetitive scientific workflows. The goal is to make future workflow runs more efficient by using provenance from past runs to select experts that are most likely to succeed. A recommender system would analyze provenance graphs to correlate input features with expert output quality and prioritize expert selection. An initial case study examines optimizing a chemistry workflow, with the recommender updating expert success rates over multiple runs to guide workflow execution. Challenges include sparse provenance data that limits recommendations, and clustering is proposed to increase data density for better optimization.