1. A non-transitory computer-readable storage medium storing a plurality of instructions for controlling a processor to build a model for diagnostics, the plurality of instructions comprising: instructions that cause the processor to determine a set of models based upon a topological relationship identifying a set of applications, a set of systems configured to execute the set of applications, and relationships between the set of applications and the set of systems; and instructions that cause the processor to generate a single aggregate model based upon the topological relationship, the aggregate model comprising the set of models and comprising one or more links between one or more of the models in the set of models, the links created based upon the relationships in the topological relationship; and instructions that cause the processor to use the single aggregate model to perform diagnostics.