Abstract: One embodiment is directed to training a machine-learning model using sample data by partitioning the machine-learning model into sub-portions and training the sub-portions in different nodes. Another embodiment is directed to training machine-learning models using features determined based on different data layers. Another embodiment is directed to determining a validity of a request for accessing data based on the processing results of policy modules. Another embodiment is directed to a policy engine including a policy knowledge module and a policy intelligence module. Another embodiment is directed to a smart data warehouse using natural language processing and nested heterogeneous graphs to visualize results.