SQL Server 2005 Integration Services (SSIS) is a new Extract, Transform, and Load (ETL) tool that ships with SQL Server 2005. As with many of Microsoft's development tools, you can extend SSIS to perform other operations not already bundled with the product. SSIS provides the SSIS Class Library for just this purpose. The SSIS Class Library Object Model includes all the classes and interfaces you need to extend or augment SSIS.
The article continues at