ABSTRACT
When systems developers build information systems, they usually do not start with a clean slate. Often, they are replacing an existing application. They must always determine if the existing information should be preserved. Usually, the older information is transferred to the new system — a process known as data conversion in previous days, but now more often called “extract, transform, and load” (ETL). This ETL process may be a onetime transfer of data from an old system to a new system, or part of an ongoing process such as is found in data warehouse and data mart applications. In fact, any time that data interoperability is an issue, similar considerations apply. Even business-to-business (B2B) and electronic data interchange (EDI) have some similar characteristics, particularly with regard to the issue of definition of common semantics, and applying business rules against the data to ensure quality. ELT can involve moving data from flat file systems to relational database management systems (RDBMS). It could also be related to changing from systems with loose constraints to new systems with tight constraints.
