1. A computer, comprising: a memory; and a data structure to store a schema for a generic document, the data structure stored in the memory and including: a definition of a first element, the definition of the first element including an element value field; and a key identifier to identify a key value field to be used as a key in a data store, wherein: the key identifier identifies the key value field as a foreign key for the data store; and the key identifier references a second data store.