Expressing a Graph
HDF5 file structure is not a tree, it is a rooted, directed graph. It may have ‘loops’, objects may have > 1 parent, ɭ name, etc.
XML enclosure maps nicely to a tree, but can’t express a graph or multiple parentage.
Solution: several possibilities, see [5]
Our approach: include the object in the tree once, use pointers for subsequent instances