Near Similarity Search and Plagiarism Analysis

Abstract

Existing methods to text plagiarism analysis mainly base on “chunking”, a process of grouping a text into meaningful units each of which gets encoded by an integer number. Together theses numbers form a document’s signature or fingerprint. An overlap of two documents’ fingerprints indicate a possibly plagiarized text passage. Most approaches use MD5 hashes to construct fingerprints, which is bound up with two problems: (i) it is computationally expensive, (ii) a small chunk size must be chosen to identify matching passages, which additionally increases the effort for fingerprint computation, fingerprint comparison, and fingerprint storage.

This paper proposes a new class of fingerprints that can be considered as an abstraction of the classical vector space model. These fingerprints operationalize the concept of “near similarity” and enable one to quickly identify candidate passages for plagiarism. Experiments show that a plagiarism analysis based on our fingerprints leads to a speed-up by a factor of five and higher—without compromising the recall performance.