As might be expected, the standards activity in this area is based on extensions to the
SQL standard. The national standards bodies have been working on object extensions to
SQL since 1991. These extensions have become part of the SQL standard, with releases in
1999, referred to as SQL:1999, and 2003, referred to as SQL:2003. These releases of the
SQL standard are an ongoing attempt to standardize extensions to the relational model and
query language. We discuss the object extensions to SQL in some detail in Section 28.4.
In this book, we generally use the term SQL:2003 to refer to both the 1999 and 2003
releases of the standard