1. An evaluation method for determining an evaluation score of one data object based on evaluation scores of and links in related data objects, the links each permitting one data object to point to another data object, the evaluation method comprising: updating, by a processor and in response to an update made to a first data object, the evaluation scores of one or more second data objects linked from at least the first data object and the evaluation scores of data objects which are linked from the first data object via the second data objects, based on the evaluation score of the first data object; and determining, by the processor and in response to a reference request for one data object, the evaluation score of the requested data object, based on the evaluation scores of one or more third data objects having a link to the requested data object and the evaluation scores of data objects which link to the requested data object via the third data objects; wherein the updating includes selecting data objects, whose evaluation scores are to be updated, based on a ratio of a change in evaluation score of other data objects against a change in evaluation score of the first data object; and the determining includes selecting data objects, whose evaluation scores are to be used to determine the evaluation score of the requested data object, based on a ratio of how much part of evaluation scores of other data objects affects the evaluation score of the requested data object.