Abstract-Plagiarism has become a serious problem mainly because of the electronically available documents. An online document retrieval is weighty part of a modern anti-plagiarism tool. This paper describes an architecture and concepts of a realworld document retrieval system, which is a part of a general anti-plagiarism software. A similar system was developed as a part of nationwide plagiarism solution at Masaryk University. The design can be adapted into many situations. Provided recommendation stem from experience of the system operation for several years. The proper usage of such systems contributes to gradual improvement of the quality of student theses.

Abstract-Plagiarism has become a serious problem mainly because of the electronically available documents. An online document retrieval is a weighty part of a modern antiplagiarism tool. This paper describes an architecture and concepts of a real-world document retrieval system, which is a part of a general anti-plagiarism software. Up to date systems for plagiarism detection are discussed from the source retrieval perspective. The key approaches of source retrieval are compared. The system recommendations stem from design, implementation, and several years of operation experience of a nationwide plagiarism solution at Masaryk University in the Czech Republic. The design can be adapted to many situations. Proper usage of such systems contributes to the gradual improvement of the quality of student theses. 

Abstract. The sliding window concept is a common method for computing a profile of a document with unknown structure. This paper outlines an experiment with stylometric word-based feature in order to determine an optimal size of the sliding window. It was conducted for a vocabulary richness method called 'average word frequency class' using the PAN 2015 source retrieval training corpus for plagiarism detection. The paper shows the pros and cons of the stop words removal for the sliding window document profiling and discusses the utilization of the selected feature for intrinsic plagiarism detection. The experiment resulted in the recommendation of setting the sliding windows to around 100 words in length for computing the text profile using the average word frequency class stylometric feature.

One of the toughest problems to solve when deploying an enterprise-wide full-text search system is to handle the access rights of the documents and intranet web pages correctly and effectively. Post-processing the results of general-purpose full-text search engine (filtering out the documents inaccessible to the user who sent the query) can be an expensive operation, especially in large collections of documents. We discuss various approaches to this problem and propose a novel method which employs virtual tokens for encoding the access rights directly into the search index. We then evaluate this approach in an intranet system with several millions of documents and a complex set of access rights and access rules.

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