1. A data processing apparatus, comprising: a data analyzer configured to analyze input data comprising a graph structure, and to verify at least one of a precondition and a post-condition of each node included in the input data; an interface generator configured to allocate a different shaped interface for each type of the precondition and the post-condition, and to allocate a node interface for the each node; and a display unit configured to display the input data based on the allocated interfaces, wherein the interface generator allocates a high complexity shape in response to a frequency of a condition being high.