1. A method of managing documents in a document management system (DMS), comprising: receiving a request to apply a document transformation to a source document managed by the DMS, wherein the document transformation specifies a set of rules to transform the source document into a result document; identifying a constituent set of document fragments in the source document; upon determining that one of the document fragments, from the set of document fragments, has been modified since a last time the document transformation was applied to the source document applying the document, transformation to only the modified fragment to generate a transformed result fragment; and storing the transformed result fragment in a result fragment cache.