EOS+CTA WorkFlows: Tape Archival and Retrieval

<!--HTML-->The CERN Tape Archive (CTA) is the tape back-end to EOS. EOS provides an event-driven interface, the WorkFlow Engine (WFE), which is used to trigger the processes of archival and retrieval. When EOS is configured with its tape back-end enabled, the CREATE and CLOSEW (CLOSE Write) events are used to trigger the archival of a file to tape, while the PREPARE event triggers the retrieval of a file from tape and the creation of a disk replica. This talk will present the details of these tape-related workflows, including the state machine for the processes of archival and retrieval, and the metadata which is communicated between EOS and CTA.