1. A model verification system built with a computer system including a processor, a storage section, an input part, and an output part, the model verification system comprising: a pattern accumulation part built with the storage section, and configured to acquire an original model figure data registered as a design pattern in association with a program by the input part; a formal language conversion part operated with the processor and configured to convert the original model figure data registered into formal language expression data based upon an expression format of a predetermined formal language; a formal language increment part operated with the processor, and configured to add formal language expression data of a derivative design by adding a modification to a component of the formal language on the converted formal language expression data, and to store the formal language expression data of the derivative design to the pattern accumulation part; and the output part can output the formal language expression data of the derivative design; and wherein the model verification system, further comprises: a design extraction part which includes: determining an information description expression format into which the model figure data, which are existing designed data, are converted based upon an extension and/or type information defined at a header of a file, extracting a parameter that specifies the model figure among the model figure data from characteristics of the determined information description expression format; generating information description expression data based upon the parameter extracted, and determining whether or not the formal language expression data is matched with the information description expression data; a quantification part which includes: storing a pattern ID and an instance ID included in a determination result where the matching has been determined; acquiring existing design log data that are matched with the instance ID managed by a matching pair management part, and acquiring a recommended Key performance indicator (KPI) range value and a KPI calculation function that match the pattern ID managed by the matching pair management part and applying the existing design log data to the recommended KPI range value and calculating a KPI value of the information description expression data; a separation part which includes: comparing KPI values that are equivalent and comparable in a plurality of pieces of the information description expression data quantified by the quantification part, setting information description expression data having a high KPI value as a replacing candidate, setting other information description expression data as a replaced candidates, and store the relationship between the candidates, and calculating a ratio of KPI values of the replacing candidate and the replaced candidates and Return On Investment (ROI) value in a case of the replacement.