HDF5 Technical Notes consist of special topics in HDF5 and technical and historical notes. Many of these topics get folded into the documentation. See HDF5 Technical Notes on the old support web site for archived information.
Query and Indexing in HDF5 (RFC)
The Query and Indexing in HDF5 feature introduces objects and APIs for querying HDF5 containers and for creating indexes on the contents of HDF5 containers.