Data Models (structures) for use with the Processing Function Library

Document all existing data models used in the processing function library (visibilities, uvws, images, source models...). Socialise as part of the processing CoP. Internal refactoring to simplify using data structures and ensure consistency (try to eliminate magical constants) Demonstrate value from refactored data models by adding utility processing functions (to be discussed - weighting, phase rotation...?)

The data models used within the Processing function library (PFL) are accessible in the PFL documentation here ( https://developer.skao.int/projects/ska-sdp-func/en/latest/data_models.html ). The processing function library was refactored to use these models on interfaces, and the models used were presented and discussed on multiple instances of Processing CoP. Data models were presented on processing CoP 2022-06-27(Sprint 15.1) ( https://confluence.skatelescope.org/display/SE/2022-06-27%28Sprint+15.1%29+Processing+CoP+Meeting+Notes ). Discussion followed with particular focus on the question of Sky Coordinates and suitable representation of these within data models. Based on discussions (thanks to Andreas Wicenec and Tammo Dijkema) the SkyCoord object was implemented into PFL ( https://developer.skao.int/projects/ska-sdp-func/en/latest/sky_coord.html ). This is compatible with SkyCoord from astropy and astropy SkyCoord object can be used as an argument in the PFL interfaces (discussion on what type of coordinates will be used by PFL is required). A phase rotation processing function was added that demonstrates the usage of the data models ( https://developer.skao.int/projects/ska-sdp-func/en/latest/proc_func_phase_rotation.html ).