1. A method of visualizing a relationship of attributes in data records, comprising: for plural categorical values of a first attribute, selecting, by a system having a processor, more relevant categorical values of a second attribute from among candidate categorical values of the second attribute, wherein the selecting uses a relevance determination process that considers frequencies of occurrence of respective pairs of the categorical values of the first and second attributes; and generating, by the system, a visualization that includes groups of cells corresponding to the respective pairs of categorical values of the first and second attributes, each of the cells corresponding to a pair of categorical values of the first and second attributes in a respective data record, wherein at least one of the groups includes cells assigned visual indicators based on values of a third attribute.