Webby is an online automatic grading system developed using open source software development tools. Its front end is a web interface developed using PHP and deployed using Apache web daemon running on Linux. The system currently grades C++ programs using standard stream I/O. All submitted C++ programs are kept in a structured directory system while grade records are stored in an SQLite database. The system grades all student-submitted programs based on a teacher-defined assessment criteria. Each criterion is assigned a percentage weight. All weights add up to 100%. Each criterion is assigned a set of input files that would sufficiently check whether a student-submitted program meets the said criterion. Part of the system is a similarity measure of any pair of student-submitted programs. The similarity measure of two programs is computed based on two things: (1) length of the longest common subsequence of token stream generated from each of student-submitted programs and (2) an approximation of a teacher’s rating of how similar two sutudent-submitted programs are. The similarity measure provides an indicator of possible plagiarism or how much work is added to a student-submitted program given a teacher-prepared program template. In this paper, we discuss the design, implementation, use, and evaluation of a working prototype of Webby.
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