3 | CONCLUSION
This paper summarizes the technical aspects of new prediction categories in CASP15 and can serve as a reference point for future predictors. The systems for handling RNA/ligand/multimer-EMA predictions in CASP15 were implemented shortly before the start of the experiment and, as such, were not extensively tested. Based on the feedback from CASP15 assessors and predictors, we plan to improve the system by further automating the process of verifying RNA and ligand submissions and ensuring better compliance of models with the required format. This investment of time and effort should pay off at the assessment stage with a more seamless evaluation of predictions. Since the PDB format is becoming obsolete, we will motivate predictors and developers of the evaluation measures used in CASP to support the PDBx/mmCIF format in their tools and methods. For the RNA category, we will work to further incorporate and standardize evaluation measures which assess the base-base interaction network. This will require setting community-accepted standards in identification and annotation of RNA interactions22. Further, we will work to improve measures comparing predictions to raw data to assess low-resolution targets. For the ligand prediction category, we need to improve the set of targets with more interesting ligand modeling challenges, possibly by tapping into unreleased structures from pharmaceutical companies. We will also improve the acceptance system by validating the identity of submitted ligands in a more robust manner, and we would like to consider introducing metrics for self-assessment of the accuracy of ligand poses within the receptor. For evaluating ensembles of alternative conformations, we will explore acceptance of multi-model entities, with optional probability weights, as submissions.