Method and apparatus for providing schema evolution without recompilation

摘要

A method and apparatus that allow schema version evolution to occur without requiring applications that expect older schema versions to be recompiled is provided. According to one aspect of the invention, each application that requests data is supplied the data in the format that the application expects. To supply the data in the expected format, a mechanism is provided for tracking the evolution of data types without losing information. In addition, mechanisms are provided for determining the format expected by the application and the format in which the data is currently stored. A mechanism is also provided for converting the data from the stored format to the expected format when the two formats do not match. A data migration strategy is described in which data is gradually migrated to newer formats when the data is updated by applications that expect a more recent format than the format in which the data is currently stored.