Lex de Haan studied applied mathematics at the University of Technology in Delft, the Netherlands. His experience with Oracle goes back to the mid-1980s, version 4. He worked for Oracle Corporation from 1990 to 2004 in various education-related roles, ending up in Server Technologies (product development) as senior curriculum manager for the advanced database administration curriculum. In that role, he was involved in the development of Oracle9i and Oracle Database 10g. In March 2004, he decided to go independent and founded Natural Join B.V. (http://www.naturaljoin.nl). From 1999 until his passing in 2006, he was involved in the ISO SQL language standardization process, as a member of the Dutch national body. He was also one of the founding members of the OakTable network (http://www.oaktable.net).
Toon Koppelaars studied computer science at the University of Technology in Eindhoven, The Netherlands. He is a veteran Oracle technology user, having used the Oracle DBMS and tools since 1987. During his career he has been involved in both application development and database administration. His experience encompasses solutions involving terminals and hosts, two-tier client-server applications, and modern-day Java Enterprise Edition and web development. His interest areas include performance tuning (ensuring scalability, SQL-tuning), architecting applications in a DBMS-centric way, and logical/physical database design. Within the database design area, the formal specification and robust implementation of data integrity constraints (often referred to as business rules) is one of his special interest areas. Toon is a frequent presenter at Oracle-related conferences, a member of the Oaktable Network (www.oaktable.net), and a coauthor of the books Applied Mathematics for Database Professionals (Apress 2007) and Leerboek Oracle SQL (in Dutch, Academic Service 2013).