1. An information processing device comprising: an input section for inputting a plurality of symbol strings and attribute information desired to be extracted from each symbol string; a feature quantity function generation section for selecting a plurality of functions from a predetermined function group including a function for converting a symbol string into a numerical value, and generating a plurality of feature quantity functions for outputting a feature quantity from the symbol string by combining the plurality of functions; a feature quantity calculation section for inputting each symbol string input by the input section to each feature quantity function generated by the feature quantity function generation section and calculating a feature quantity corresponding to each symbol string; an estimation function generation section for executing machine learning using the attribute information corresponding to each symbol string input by the input section and the feature quantity corresponding to each symbol string calculated by the feature quantity calculation section, and generating an estimation function for estimating the attribute information from the feature quantity; and an output section for outputting the feature quantity functions generated by the feature quantity function generation section and the estimation function generated by the estimation function generation section.