iRODS manages unstructured data. Generally, this means files, but iRODS can manage other types of data as well. This is data that doesn’t fit directly into the relational database paradigm. However, iRODS makes extensive use of a relational database to link unstructured data to metadata. We recognize that there already exist several very capable relational databases. So, iRODS works with your choice of a number of prominent, externally-developed relational databases.