1. A computer-implemented method of guiding a user in designing a product defined by data, the method comprising: examining, by a processor, items of data to detect whether each item conforms to rules; performing, by the processor, an action in response to a detection of a rule violation; displaying, by the processor, the data items in a tabular format including cells and in a manner emphasizing a first data item that caused the rule violation and emphasizing a second data item that existed prior to the first data item but that is associated with the rule violation caused by the first data item, the action comprising the displaying; receiving, by the processor, a control input from a user; and in response to receiving the control input from the user, automatically changing, by the processor, the second data item to one of a plurality of possible values for the second data item, the one of the plurality of possible values being selected by the processor to cause the rule violation to be corrected.