The HDF5 file is organized into six hierarchy levels. These are called the Bundle, Slice, Grid, Topology, Representation and Field levels. The Bundle group is the toplevel group, i.e. the HDF5 file itself. Subgroups with a time attribute constitute a Slice group, which contains all data related to a specific time.
A Slice group may contain many geometrical objects, called "Grids". The name of this group is arbitrary, each Grid group contains a self-consistent geometrical entity (e.g. a uniform grid with refinement levels, a triangular surface, a tetrahedral grid, an adaptive mesh with all refinement levels).
A Grid will be described by one or many datasets. All datasets within a Grid which are of the same size and dimensioniality and are semantically related to the same indexing scheme (e.g. all data fields within a given AMR refinement level, or data given on the cells of a tetrahedral grid) are grouped together into Topology groups.
Data sets within Topology groups are further organized into Representation groups according to their relationship to other objects. The name of the Representation group (and possible attributes) tell the relation of a certain data set, e.g. a Representation group may be named "cartesian chart 3D" or "parent level".
1.6.2