1. A data processing system which processes object data in response to a designation, comprising: a manager configured to manage the object data together with object attribute information indicative of an attribute thereof; a designator configured to designate a processing with respect to the object data through a dialog operated by a user; an execution unit configured to execute the processing of the object data in response to a designation performed by the designator; and a first result predictor configured to execute, when the dialog is operated by the user, a prediction on a result of the processing by comparing subject attribute information, which indicates an attribute of another processing to be executed by the execution unit, with the object attribute information, and to output, to the user, prediction notification information in accordance with the result of the processing obtained through the prediction, wherein the designator includes a designation alteration coping portion configured to generate a new designation in accordance with a dialog operated by the user after the prediction notification information is outputted, wherein, where the processing unit is a terminal which combines a plurality of object data by combining the object data with other object data in a manner that the former and latter object data are determined as combine-source and combine-destination, respectively, the first result predictor predicts a result of the processing by performing comparison between: object information of the object data of the combine-destination, in addition to the subject attribute information of the terminal; and the object attribute information of object data of the combine-source.