In recent years, declarative, constraint-based approaches have been proposed to model loosely-structured business processes, mediating between support and flexibility. A notable example is the Declare framework, equipped with a graphical declarative language whose semantics can be characterized with several logic-based formalisms. Up to now, Declare constraints have been mainly used to tackle control-flow aspects, abstracting away from data. In this work, we extend Declare so as to include task data and data-aware constraints. We show how the Event Calculus (EC) formalization of Declare can be improved to deal with such extensions, and to apply a reactive EC reasoner for monitoring data-aware constraints