Oracle Workflow provides a sql script that defines the WF_USERS, WF_ROLES, and WF_USER_ROLES views that map to this unified environment. When you install Oracle Applications, you automatically install this script to create the unified environment. However, if you should need to edit and rerun this script for whatever reason, the script is called wfdirhrv.sql and is located on your server in the admin/sql subdirectory under $FND_TOP.
Aside from the users and roles stored in WF_LOCAL_USERS and WF_LOCAL_ROLES, the default notification preference for all workflow users and roles in the unified environment is set to 'MAILHTML'.
See: Setting Up an Oracle Workflow Directory Service