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Author: Kavanagh, John
Section: Career moves
Dublin City University finds new way to detect software plagiarism
computer.weekly@rbi.co.uk
A way of detecting
software plagiarism which uses spaces and tabs instead of code
comparisons has found 36% of computing students at Dublin City
University copying programs from fellow undergraduates.
The method, described
in BCS academic publication The Computer Journal involves inserting
into a program a 34-bit field including a student identity, the
student's year of entry to the university, the assignment identity and
other information.
The data is coded using a space to represent zero and a tab to represent one.
"The data appears as
blank space, and is unlikely to be changed if the program is modified,"
said researchers Charlie Daly and Jane Horgan of the School of
Computing at Dublin City University.
"In addition,
generally, text editors do not show excess white space at the end of a
line. This fingerprint, or watermark, can be used to ascertain who
originally submitted the program and who submitted a copy.
"Existing source code
comparison methods are reasonably successful at grouping similar
submissions but they have no way of distinguishing between the author
and the copier.
The researchers
added, "This method works even when the program has been extensively
modified, as long as the watermark remains undisturbed.
"It can detect
copying in very short programs. With such programs students may come up
with similar solutions by chance. Source code comparison systems cannot
distinguish chance similarities from cases of copying.
"The method requires
no manual intervention. By contrast, code comparison techniques merely
highlight suspicious cases, which then need to be examined to determine
whether plagiarism has occurred. Naturally, this is subjective, as well
as tedious and time consuming."
The method only works
if the copier makes an electronic copy rather than keying in the
program again, because the watermark will not be keyed.
The method was tested
on 46 programming exercises completed by 283 students in the first year
of a computing degree course at Dublin City University.
It found that 101
students (36%) had copied at least one of the exercises. Most copied
one or two, but some were more active, including one student who copied
19 of the 46 exercises. In addition, 48 students (17%) allowed others
to copy their programs.
The copying increased
during the year. Daly and Horgan said this might be down to students
leaving the work to the last minute and therefore becoming more tempted
to copy.
"The results are of
additional interest in view of warnings about plagiarism given to
students at the beginning of the course," they said.
The research found
that crime does not pay: the copiers got an average mark of 37%. The
people they copied from got an average of 58%, and those who were not
involved in any way got 51%.
The difference in
marks between the last two groups is not surprising, according to Daly
and Horgan. "Copiers may be dishonest but they are not stupid, and will
choose their suppliers carefully," they said.
~~~~~~~~ By John Kavanagh
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