public interface DataSourceOperations
operation that
 acts on the set of stored objects represented by a DataSource,
 performing one of the basic actions that makes sense on a set of similar records: "fetch",
 "add", "update" or "remove".  There is also a fifth DataSource Operation, "custom", which is
 intended for arbitrary server operations that are more complex than a fetch of some records, or
 an update to a single record. Each DataSource operation has specific request and response data, for example, in the "fetch" DataSource operation, the request data is expected to be search criteria, and the response data is expected to be a list of matching DataSource records. Listed below are the request data and response data for each DataSource operation type, and what they mean.
DataSource records are represented on the client by a JavaScript Object, where each property in the Object maps a DataSource field name to the field value - hence the DataSource operations below are in essence a way of exchanging records from client to server and back.
 If you are using server-side data integration with the Smart GWT Java server, see the  Java
 Server Reference  for information about how DataSource Requests arrive on the server
 (specifically com.isomorphic.datasource.DSRequest) and how to provide responses  (specifically
 com.isomorphic.datasource.DSResponse.setData()). 
 If you are using client-side data integration to directly
 consume services that use XML, JSON or other formats, see the "Editing and Saving" section of
 the client-side data integration topic.
 
fetch
DSRequest.oldValues as the source for whatever
 criteria values you need.  That covers everything except AdvancedCriteria.