The EO_SOURCE_FEATURE table is the database link between EO and Source Feature records. In addition to the "foreign key" columns eo_shape_id and source_feature_shape_id from the SHAPE table, it now also contains eo_id from EO and source_feature_id from SOURCE_FEATURE.
These fields were added and populated during conversion to Biotics 5, and should make queries involving EOs and Source Features easier!