Plagiarism Detection Software Entrails: How Machine Could Check My Writing?

Using Software for Plagiarism Detection

According to the Merriam-Webster Online Dictionary the meaning of the word “plagiarize” is to steal and pass off the ideas of another person as your own; to use another’s production without crediting the source; to commit literary theft; to present as new and original an idea or product derived from an existing source.

The two most common types of plagiarism are textual plagiarisms and source code plagiarism. [1]. Plagiarism detection can be either manual or software assisted. Software plagiarism detection is referred to as PDS or plagiarism detection systems.

The approach to plagiarism detection using a PDS will be either:

  • An external detection system: Compares suspicious documents with a reference collection of a set of documents. Using a pre-determined similarity criteria threshold, the suspect document is compared to the reference document set. The system will pull any document that exceeds the similarity threshold of the suspect document for further inspection
  • An intrinsic plagiarism detection system: Analyzes only the text to be evaluated. No comparison is made with external documents. The approach recognizes changes in the unique writing style of an author and considers them an indicator for potential plagiarism. [2]

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Plagiarism Detection Techniques and Methods

  • plagiarism detection softwareFingerprinting: Fingerprinting is an external detection system and the most widely used plagiarism detection method. A document to be checked will have its fingerprint computed and compared to other document fingerprints. If the predetermined similarity threshold is exceeded it suggests the possibility of plagiarism. [2]
  • String matching: Documents are compared for verbatim text overlaps. Checking a document using string matching requires a fair bit of computing power and isn’t a viable option if there a large number to be checked. [3]
  • Citation Based Plagiarism Detection: This method examines the citation and reference information that is contained in texts in order to identify similar patterns in the citation sequences. This method is well suited for scientific texts, or other documents containing citations. [4]

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A Brief History of Source Code Plagiarism Detection

The following is a little background history of source code plagiarism detection:

  • 1976: The first source-code software for plagiarism detection was developed by Ottenstein to detect plagiarism in FORTRAN programs. It was an attribute-counting system that used Halstead’s software metrics consisting of four numbers. These numbers were used to calculate five attributes. Ottenstein asserted that the probability of two programs written independently having the same attributes was very small and an indication of plagiarism.check my writing
  • 1980: Robinson and Soffa develop a new system named ITPAD (Instructional Tool for Program Advising). It was designed to help with the assessment process of FORTRAN programs by verifying the quality of the code, detecting possible plagiarism and making suggestions on how code could be improved.
  • 1981: Donaldson, Lancaster and Sposato create the first detection system using structure-metrics. The software used attribute-counting metrics but also scans the source file to store information about several types of statements.
  • 1990: Software called “Plague” is developed by Whale. It generates structure profiles from the input programs composed of structural information and transforms the code into sequences of tokens.
  • 1996: Wise creates an algorithm called Running-Karp-Rabin Greedy-String-Tiling to match sequences of tokens. The algorithm is used in a system called YAP3 that is still being used today.
  • 2000: JPlag is presented by Prechelt. It transforms the programs into sequences of tokens and compares the sequences with the Greedy-String-Tiling algorithm to determine similarity.[5]

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How Plagiarism Detection Software Works

To check my writing for plagiarism using software is relatively easy from the operators perspective. Usually you just copy your text into the appropriate area and run the program. There are a number of different ways that software may used to detect plagiarism. Typically the following is what happens when running the software program:

  • plagiarism detection techniquesThe software uses a complex mathematical process that converts the document into a unique string. This string is known as a fingerprint. A string may have many substrings. Basically the more substrings there are the more detailed the fingerprint. The more detailed the fingerprint the more accurate it will be in detecting plagiarism. However more processing power will be required
  • The document fingerprint is taken and compared to a library of other document fingerprints which will likely number in the millions. If a document exhibits a high degree of similarity a closer comparison should be made
  • Depending on the software, if two documents are similar enough a second comparison will be made only this time string matching will be used as there will be only a few documents to check. [6]

A combination of plagiarism detection methods is usually more accurate than just one but it depends on the software you have. The best plagiarism detection software is fast accurate and affordable but that isn’t always easy to find.


[1] Hermann Maurer, Frank Kappe, Bilal Zaka “Plagiarism – A Survey” Institute for Information Systems and Computer Media Graz University of Technology, Austria, vol. 12, no. 8 2006

[2] Stein, B., & Meyer zu Eissen, S. (2006). Near similarity search and plagiarism analysis. In Proceedings of the 29th Annual Conference of the Gesellschaft für Klassifikation e.V. (pp. 430–437). Magdeburg: Springer.

[3] International Journal for Educational Integrity Vol. 9 No. 1 June, 2013 pp. 50–71 ISSN 1833-2595

[4] International Journal of Innovative Research in Advanced Engineering (IJIRAE) ISSN: 2349-2163 Volume 1 Issue 7 (August 2014)


[6] https://www.plagiarismtoday.com/2016/05/03/plagiarism­detection­works/