Data Warehousing Systems: Foundations and Architectures

SYNONYMS None DEFINITION A data warehouse (DW) is an integrated repository of data for supporting decision-making applications of an enterprise. The most widely cited definition of a DW is from Inmon [3] who states that " a data warehouse is a subject-oriented, integrated, nonvolatile, and time-variant collection of data in support of management's decisions. " HISTORICAL BACKGROUND DW systems have evolved from the needs of decision-making based on integrated data, rather than an individual data source. DW systems address the two primary needs of enterprises: data integration and decision support environments. During the 1980s, relational database technologies became popular. Many organizations built their mission-critical database systems using the relational database technologies. This trend proliferated many independent relational database systems in an enterprise. For example, different business lines in an enterprise built separate database systems at different geographical locations. These database systems improved the operational aspects of each business line significantly. Organizations, however, faced the needs of integrating the data which were distributed over different database systems and even the legacy database systems in order to create a central knowledge management repository. In addition, during the 1990s, organizations faced increasingly complex challenges in global environments. Organizations realized the need for decision support systems that can analyze historical data trends, generate sophisticated but easy-to-read reports, and react to changing business conditions in a rapid fashion. These needs resulted in the development of a new breed of database systems that can process complex decision-making queries against integrated, historical, atomic data. These new database systems are now commonly called data warehousing systems because they store a huge amount of data – much more than operational database systems – and they are kept for long periods of time. A data warehousing system these days provides an architectural framework for the flow of data from operational systems to decision-support environments. With the rapid advancement in recent computing technologies, organizations build data warehousing systems to improve business effectiveness and efficiency. In a modern business environment, a data warehousing system has emerged as a central component of an overall business intelligence solution in an enterprise.