If you mean root cause as in TPM for factory equipment, in my company we use a customised package.
The 2 main features are:
(1) How we code the list of reasons. (WHY-WHY). It is a "tree-view" which flows basically from the equipment manufacturer's instruction and training material and our own knowledge base and we don't bother about stuff like "levels" or other classic BOM and costing stuff or redundancy. (It was a conscious decision supported by an IS expert).
(2) The exception is related schedules and instructions on the same machine. Eg. For a machine we could need to monitor and manage 2 gauges and a fuse in addition to it's main function.
Aggregation is another issue.
HTH.
End of mail.