University of Hertfordshire

By the same authors

Same Difference: Detecting Collusion by Finding Unusual Shared Elements

Research output: Contribution to conferencePaper


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Original languageEnglish
Number of pages25
Publication statusPublished - 2012
Event5th International Plagiarism Conference - Sage Gateshead, Newcastle, United Kingdom
Duration: 17 Jul 201218 Jul 2012


Conference5th International Plagiarism Conference
CountryUnited Kingdom
Internet address


Many academic staff will recognise that unusual shared elements in student submissions trigger suspicion of inappropriate collusion.
These elements may be odd phrases, strange constructs, peculiar layout, or spelling mistakes. In this paper we review twenty-nine approaches to source-code plagiarism detection, showing that the majority focus on overall file similarity, and not on unusual shared elements, and that none directly measure these elements. We describe an approach to detecting similarity between files which focuses on these unusual similarities. The approach is token-based and therefore largely language independent, and is tested on a set of student assignments, each one consisting of a mix of programming languages. We also introduce a technique for visualising one document in relation to another in the context of the group. This visualisation separates code which is unique to the document, that shared by just the two files, code shared by small groups, and uninteresting areas of the file.


Pam Green, Peter Lane, Austen Rainer, Sven-Bodo Scholz, Steve Bennett, ‘Same Difference: Detecting Collusion by Finding Unusual Shared Elements’, paper presented at the 5th International Plagiarism Conference, Sage Gateshead, Newcastle, UK, 17-18 July, 2012.

ID: 2142713