A cloud-based diagnosis and maintenance system facilitates discovery and indexing of plant-wide data residing on various data platforms across multiple industrial facilities. The system includes an indexing system that automatically inventories industrial devices and other data sources located throughout the facilities, and identifies available data items on each data source. The indexing system indexes the discovered data items in a federated data model that can subsequently be searched to locate data items or tags of interest. The diagnosis and maintenance system also includes analysis tools that facilitate cross-facility analysis of the data model, allowing performance metrics to be compared across similar automation systems at different facilities. The system can also generate recommendations for improving performance metrics based on results of the comparative analysis.