A data storage and retrieval system for a computer memory configured according to a document store adapted to contain documents. The document store includes a document data structure containing a header and a document having one or more members. The document store further includes a chain of one or more differential data structures, each having a header and at least one updated member. The updated member has a value which is updated relative to a value in a corresponding member having a same identifier in the document data structure or in a preceding differential data structure in the chain. A header of each of the differential data structures includes a pointer to the document data structure or the preceding differential data structure in the chain, and a flag indicating that each of the differential data structures contains less than all of the members of the document data structure.