1. A method of converting a system model with use of a computer in order to facilitate analysis and editing of a system model, the computer including a graph model storage unit for storing therein a graph model which is the system model having a graph-type data structure and including a plurality of model elements, the method comprising the steps of: receiving input of a conversion processing description including a description about a structure of a multi-dimensional data model and extraction queries each of which is for extracting any of the model elements; and generating the multi-dimensional data model in which dimensions have a hierarchical relationship, from the graph model stored in the graph model storage unit on the basis of the inputted conversion processing description.