Keys

Identify data inside a Daf data set using a key. These types are used in various high-level API parameters.

A separate key space is used for axes and data; thus, both axes and scalars use a simple string key.

A key specifying some axis in Daf by its name.

A key specifying some scalar in Daf by its name.

A key specifying some vector in Daf by its axis and name.

A key specifying some matrix in Daf by its axes and name. The axes order does not matter.

A key specifying some atomic data property in Daf . That is, these keys refer to data we can directly get or set using the APIs.

A key specifying some tensor in Daf by its axes and name. Daf is restricted to storing 0D, 1D and 2D data, for good reasons; higher dimensional data raises sticky issues about layout and there is no support for any sparse representation (which is even more important for this kind of data). However, sometimes it is necessary to store 3D data in Daf . In this case, we pick the 1st axis as the main one, and store a series of <main-axis-entry>_<property_name> matrices using the other two axes (whose order doesn't matter). Access is only to each specific matrix, not to the whole 3D tensor. However, it is useful to be able to specify the whole set of matrices for copying, views, contracts, etc.

A key specifying some data property in Daf . This includes TensorKey which actually refers to a series of matrix properties instead of a single data property.