# HDF5

We are starting with hdf5 because our initial test case is the [NWB](https://www.nwb.org/) format for neurophysiology data. This is a challenging initial test case because the data is heterogeneous, large, and the specification is written in an idiosyncratic format specification. 

HDF has three primary types of objects:
- Groups
- Datasets - contain the raw values in the file
- Attributes - metadata about groups or datasets.

Datasets have additional properties:
- Datatypes: binary representation of the data
- Dataspaces: Layout of individual data elements
- Properties: Additional information about the representation of the dataset, eg. chunked or contiguous

These map naturally onto triplets, where each group or dataset is a subject, attributes are properties and objects.