North52 Business Process Activities (BPA) exists as a managed solution within Dynamics 365. This managed solution contains both the business rules engine & the HTML5 editors to create the business rules.

The architecture of North52 BPA is built using plugin's which are a standard extensibility point of Microsoft Dynamics 365 . The diagram below shows how North52's BPA integrates with the Dynamics 365  platform. North52 BPA loads all the active formulae you have defined in your Dynamics 365 system into memory & then effectively listens for a user action and will execute a formula when required. 

You can effectively daisy chain formulae together by setting the Execution Order field on formulae that are all related to one entity, pipeline stage & pipeline event combination.