Speaker
Description
RNTuple is ROOT's next-generation columnar format, replacing TTree as the primary storage solution for LHC event data.
After 6 years of R&D, the RNTuple format reached the 1.0 milestone in 2024, promising full backward compatibility with any data written from that moment on.
Designing a new on-disk format does not only allow for significant improvements on file sizes and read/write speed, but it also gives the opportunity for introducing entirely new features that were missing in TTree.
One such feature is a built-in "attribute" system that allows metadata to be reliably associated to an RNTuple.
Compared to a bespoke user-level solution, built-in attributes are self-contained, self-describing and mergeable without requiring any external context (e.g. a software framework that knows how to associate and merge those attributes).
Furthermore, the API to interact with attributes can be designed to be intuitively useable by anyone familiar with the regular RNTuple API.
This work presents a prototype implementation of the RNTuple attribute system, alongside concrete examples of its use.
Open questions for further integration with the LHC experiments' frameworks are also discussed.
Significance
This work introduces for the first time support for columnar datasets metadata in a ROOT-native format, which is currently done by users "manually", e.g. with TTree.