todd8 on A System for Detecting Software Plagiarism

Comment on A System for Detecting Software Plagiarism

I took a brief peek at the paper cited by the article (http://theory.stanford.edu/~aiken/publications/papers/sigmod...) to see how the system worked. It uses hashes of n-grams of the submitted programs to compare similarity.

My own experience with plagiarism came when teaching a university course for CS majors. For most, the class was their second course in programming. While grading an early programming assignment I noticed a program that reminded me of one of the early ones I had already graded. Comparing the two programs revealed that they were identical, except that the variable names had been changed to protect the guilty.

I wonder if this system would have detected this case of collaboration.

lightonphiriOP11y

Yes, MOSS does that.

I have been TA'ing a first year Python Programming course since beginning of this year; what you describe is the most common trick used by students---even though they have been told time and again that this will be detected.

As an example, MOSS picked up 91% similarity---between two students---for one of the module files.

  # Student 1
  at1 = input("Attempt 1:\n")
  at2 = input("Attempt 2:\n")
  at3 = input("Attempt 3:\n")
  maxi.append(max(eval(at1),eval(at2),eval(at3)))

  # Student 2
  attempt1 = input("Attempt 1:\n")
  attempt2 = input("Attempt 2:\n")
  attempt3 = input("Attempt 3:\n")
  maximums.append(max(eval(attempt1),eval(attempt2),eval(attempt3)))

I find it interesting that MOSS does a one-on-one comparison for each student.

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