Improving performance of privacy-preserving collaborative filtering schemes

Privacy-preserving collaborative filtering methods offer useful filtering skills without deeply jeopardizing individual privacy. However, they mostly suffer from accuracy, scalability, and sparseness problems. Applying privacy measures to conceal confidential data in recommendation systems causes a bias in collected data, which might make accuracy worse. As the content in recommendation domain proliferates, the size of collected data expands rapidly, which aggravates scalability challenge of those systems. In addition, since users are typically able to rate a small fraction of existing products, sparseness of collected data becomes an issue.In this dissertation, various preprocessing methods are proposed to overcome accuracy, scalability, and sparseness challenges faced by various privacy-preserving collaborative filtering systems. Through application of the proposed preprocessing techniques like item ordering and elimination, clustering, dimensionality reduction, user profiling, profile cloning, and son on, novel privacy-preserving collaborative filtering schemes are cultivated. Essentially, the proposed enhanced systems focus on producing accurate predictions while coping with constantly growing nature of collections without jeopardizing individual privacy. The proposed schemes are analyzed in terms of privacy and overhead costs. Also, real data-based experiments are performed to scrutinize their effects on accuracy, scalability, and privacy. The analysis and experimental outcomes demonstrate that the methods preserve individual privacy and offer adequately accurate recommendations in scalable amount of time.Keywords: Preprocessing; Privacy; Scalability; Accuracy; Sparsity; Collaborative ?ltering.