1. A method comprising: building a hierarchical multi-stage model of asset failure risk for complex heterogeneously distributed physical assets, said hierarchical multi-stage model considering heterogeneity of failure patterns for said assets; analyzing at least one data stream to determine whether said hierarchical multi-stage model needs to be updated due to a change in said failure patterns; and if said analysis indicates that said hierarchical multi-stage model needs to be updated, dynamically updating said hierarchical multi-stage model to obtain an updated hierarchical multi-stage model.