1. A computer-readable, non-transitory medium encoded with a program, the program causing a computer to perform a procedure comprising: storing a plurality of translation rules for different types of phrases, each translation rule describing how a phrase is to be translated into graphical symbol datasets and relationship link datasets, the graphical symbol datasets each specifying a graphical symbol with a content label representing content of the graphical symbol, the content label being or including a word contained in the phrase, the relationship link datasets each specifying a relationship link that represents a relationship between graphical symbols, the relationship link having a particular end shape to indicate a type of relationships; analyzing a statement written in a natural language to determine types and structure of phrases that constitute the statement; and translating each of the phrases constituting the statement into two or more graphical symbol datasets and one or more relationship link datasets, according to the translation rules pertinent to the determined types of the phrases.