Open PI is the first dataset for tracking state changes in procedural text from arbitrary domains by using an unrestricted (open) vocabulary. The dataset comprises 29,928 state changes over 4,050 sentences from 810 procedural real-world paragraphs from WikiHow.com. The state tracking task assumes new formulation in which just the text is provided, from which a set of state changes (entity, attribute, before, after) is generated for each step, where the entity, attribute, and values must all be predicted from an open vocabulary.