12. A feature tagging system, comprising: a code structure based description unit association model (CDAM) generation module configured to build a CDAM that associates code units with respective description units and organizes the code units in a hierarchical structure; a CDAM refinement module configured to filter the CDAM to remove un-meaningful description units from the CDAM through cross-validation between code units; and a feature tag module comprising a processor configured to generate feature tags based on a weighted sum of term frequencies in the description units of the filtered CDAM to associate features with respective code units.
12. A feature tagging system, comprising: a code structure based description unit association model (CDAM) generation module configured to build a CDAM that associates code units with respective description units and organizes the code units in a hierarchical structure; a CDAM refinement module configured to filter the CDAM to remove un-meaningful description units from the CDAM through cross-validation between code units; and a feature tag module comprising a processor configured to generate feature tags based on a weighted sum of term frequencies in the description units of the filtered CDAM to associate features with respective code units. 13. The system of claim 12 , wherein the CDAM generation module is further configured to perform fact-based association and concept-based association.