Future analysis of ATLAS data will involve new small-sized analysis
formats to cope with the increased storage needs. The smallest of
these, named DAOD_PHYSLITE, has calibrations already applied
to allow fast downstream analysis and avoid the need for further
analysis-specific intermediate formats. This allows for application
of the "columnar analysis" paradigm where operations are applied
on a per-array instead of a per-event basis. We will present methods
to read the data into memory, using Uproot, and also discuss I/O
aspects of columnar data and alternatives to the ROOT data format.
Furthermore, we will show a representation of the event data model
using the Awkward Array package and present proof of concept for a
simple analysis application.