The DataAxesFormats package provides a uniform generic interface for accessing 1D and 2D data arranged along some set of axes. This is a much-needed generalization of the AnnData functionality. The key features are:

• The data model StorageTypes include (1) some axes with named entries, (2) vector data indexed by a single axis, (3) matrix data indexed by a pair of axes, and also (4) scalar data (anything not tied to some axis).
• Explicit control over 2D data MatrixLayouts (row or column major), with support for both dense and sparse matrices, both of which are crucial for performance.
• Out of the box, allow storing the data in memory (using MemoryDaf ), directly inside HDF5 files (using H5df ), or as a collection of simple files in a directory (using FilesDaf ), which works nicely with tools like make for automating computation pipelines.
• Import and export to/from AnnDataFormat for interoperability with non- Daf tools.
• Implementation with a focus on memory-mapping to allow for efficient processing of large data sets (in theory, larger than the system's memory). In particular, merely opening a data set is a fast operation (almost) regardless of its size.
• Well-defined interfaces for implementing additional storage Formats .
• Creating Chains of data sets, allowing zero-copy reuse of common data between multiple computation pipelines.
• Concat multiple data sets into a single data set along one or more axes.
• A Query language for accessing the data, providing features such as slicing, aggregation and filtering, and making Views and Copies based on these queries.
• Self documenting Computations with an explicit Contracts describing and enforcing the inputs and outputs, and Adapters for applying the computation to data of a different format.

The Daf data sets type hierarchy looks like this:

DafReader (abstract type)
├─ DafReadOnly (abstract type)
│  ├─ DafReadOnlyWrapper (created by read_only)
│  ├─ DafView (created by viewer)
│  └─ DafChainReader (created by chain_reader)
└─ DafWriter (abstract type)
   ├─ DafChainWriter (created by chain_writer)
   ├─ MemoryDaf
   ├─ FilesDaf
   └─ H5df