关键词: 抄袭检测, 相似度, Winnowing算法, 结构度量, 属性计数

Abstract: Based on analyzing characteristics and drawbacks of the existing plagiarism detection system in program code, a hybrid plagiarism detection method combining text analysis, structure metrics and attribute counting is proposed. Firstly, the document fingerprinting technology and Winnowing algorithm are used to compute text similarity. Secondly, the program code is translated to a Dynamic Control Structure tree（DCS）, and Winnowing algorithm is applied to estimate the DCS tree similarity which is structural similarity also. Then each variable information in code is collected and counted. The variable similarity algorithm is applied to analyze variable information node and get variable similarity. Finally, the text similarity, structural similarity and variable similarity are assigned a weight to compute the total code similarity. The experimental results show that the proposed method can effectively detect all kinds of plagiarism. To the different threshold values, the accuracy and the recall ratio of test results are higher than JPLAG system. Especially for the simple structure in program code, the average accuracy of testing results of the method and JPLAG system are 82.5% and 69.5% respectively. Consequently it shows that the proposed method is more effective.

Key words: plagiarism detection, similarity, Winnowing algorithm, structure metrics, attribute counting