I'm using BMI containers with several indexes, notably an index on the parent of each entry. But some of my BMIs have a hierarchical parent-child relationship of their entries, and I need to answer hierarchical queries like is-child-of, is-descendant-of, is-ancestor-of, etc... In another use case, entries have a "scenario" key, where scenario is hierarchical, and I want all entries in BMI A from a given scenario and all its ancestors, with the scenarios being in BMI B (i.e. "cross-bmi"). Of course I can do a "full scan" but I'm looking for something hopefully faster/smarter. Has anyone experimented with providing such a specialized index? At least in one instance, I'm manually keeping a separate container with all the edges of the DAG to be able to answer such a query, but then I have to maintain this "index" separately from the BMI, which is precisely what BMI is designed to avoid. This is also a solution that is OK in this particular case (~ 1500 nodes, ~7500 edges), but may be too expensive for some other graphs with more nodes. Any input would be appreciated. Thanks, --DD