I'm not the only one who can write UNIX filters. Here are some other efforts at implimenting the concepts outlined in the UNIX Review /RDB White Paper

• No SQL by Carlo Strozzi, Italian Linux Society.
• /RDB from Revolutionary Software
• /RDB-Hobbs from RAND.
• Unity from Bell Labs.
• dbops from simtech
• jink A nice interactive table editor is available here.
• reldb by Gunnar Stefansson.
• |Stat by Gary Perlman.
• JDB