When referring to the use of metadata, a data transformation converts a set of data values from the format of an original data system into the format of a new data system.
Data transformation can be divided into two steps: data mapping and code generation. Data mapping takes data elements from the source data system and maps them to the destination data system and captures any transformation that must occur. Code generation is responsible for the written code that creates the program that will transfer data from one system to another. A good example of a data transformation is using the programming language XSLT to transfer XML documents from one literature database to another (i.e. a publisher’s database to PubMed).