1. An information processing apparatus comprising: a computer-readable recording medium, comprising: a classifying section classifying a set of attributes, which represent relationships between an input and an output of a system defined by a plurality of limiting elements, into classification levels on the basis of a tendency of the attributes by using a hierarchical clustering technique for clustering the set into hierarchy levels on the basis of the tendency; a limiting element indicating section indicating a limiting element corresponding to a classified attribute; and a comparing section comparing the indicated limiting element in a classified level with the indicated limiting element in other classified levels, wherein the comparing section extracts a common concept on the basis of the limiting element common among the hierarchy levels, wherein the limiting element indicating section constructs a cause-effect network indicative of a relationship between the limiting element and an attribute by placing the plurality of limiting elements and the attributes in a same dimension, and wherein the computer-readable recording medium further comprises a correlation coefficient calculating section which calculates a correlation coefficient indicative of a magnitude of the relationship between fulcrums when the limiting elements and the attributes are defined as fulcrums on the cause-effect network, the comparing section extracting a cause-effect network whose correlation coefficient is larger than a pre-defined value by calculating correlation coefficients between all fulcrums at the correlation coefficient calculating section.