1. A system comprising: one or more computer-readable media; a plurality of management packs embodied on the one or more computer-readable media, wherein each individual management pack comprises: a model declaration that represents an abstract model that describes components of the management pack, properties associated with the components, and relationships between the components, the components representing objects in a subsystem of a modeled system; discovery rules that describe how to find entities in a particular environment and relationships between the entities, the entities being instantiations of the objects; a monitoring policy that comprises a state machine that describes states and transitions associated with each entity of the entities; and a causality model that uses the discovery rules and the monitoring policy to express causality across the subsystem of the modeled system, wherein the causality model further: expresses causality in a manner that does not require specific knowledge of an instance of remaining management packs; and expresses multiple different reasons for an observable fault, with at least one reason being associated with a different entity in a different management pack than an entity for which causality is expressed; and a root cause analysis engine to access and utilize data generated by the causality model to determine a root cause of the observable fault based at least in part on the at least one reason expressed by the causality model.