Integration of the EventIndex with other ATLAS systems

The ATLAS EventIndex System, developed for use in LHC Run 2, is designed to index every processed event in ATLAS, replacing the TAG System used in Run 1. Its storage infrastructure, based on Hadoop, necessitates revamping how information in this system relates to other ATLAS systems. In addition, the scope of this new application is different from that of the TAG System. It will store fewer derived quantities, but store more indexes since the fundamental mechanisms for retrieving these indexes will be better integrated into all stages of processing, allowing more events from later stages of processing to be indexed than was possible with the previous system. Connections with other systems are fundamentally critical to assess dataset completeness, identify data duplication, and check data integrity, but also needed to enhance user and system interfaces accessing information in EventIndex. This presentation will give an overview of the ATLAS systems involved, the relevant metadata, and describe the technologies we are deploying to complete these connections.