Based On The Data Flow Diagram Of The Database Schema Reverse Recovery Technology Research

Software maintenance typically represents 70%of the cost during the life cycle of a system.Legacy information systems,i.e.,data-intensive applications such as business systems,based on hundreds or thousands of data files(or database tables), significantly resist modifications and changes.In such systems,it is impossible to understand a program until the main(business) data meanings have been fully understood.Generally,database data model in legacy systems are easy to get while data flow graphs that modeling the systems modular input,output and functions are missed.Therefore,recovering the data semantics in programs and data flow graphs of the system is the urgent requirement for the maintenance of data-intensive applications.Most of the current studies in software reverse engineering focus on program reverse engineering ignoring data from external files,while the researches of date reverse engineering are limited in database domain.Data assets in programs and data assets in data files are separately treated.To solve these problems mentioned above,this paper, based on the database scheme files,considering both database information and program reverse engineering techniques,proposes a method to determine the meaning of data in programs and generate the system hierarchical data flow graphs.The method first gets the semantics of data in database from database scheme,and then explores the code snippets that interact with DBMS to find the direct or indirect mapping of the program variable and the database columns utilizing the system dependency graph and string expression analysis technique.And then data semantics are assigned or transmitted according to the dependence relationships of the variables in the context.After obtaining the bottom data flow in methods(functions),this paper proposes a new criterion to cluster the modules based on the database dependencies and system call graph information.Then some clustering work is done to get layered data flow graph using this criterion.With this method,meanings of data asset in program increased,together with system data flow graph,feature location and program understanding become easy.