分布式数据库原理

In the previous chapter, we discussed top-down distributed database design, which is suitable for tightly integrated, homogeneous distributed DBMSs. In this chapter, we focus on bottom-up design that is appropriate in multidatabase systems. In this case, a number of databases already exist, and the design task involves integrating them into one database. The starting point of bottom-up design is the individual local conceptual schemas. The process consists of integrating local databases with their (local) schemas into a global d atabase with its global conceptual schema (GCS) (also called the mediated schema).