Content-based Recommender System for Detecting Complementary Products : Evaluating Siamese Neural Networks for Predicting Complementary Relationships among E-Commerce Products

Abstract: As much as the diverse and rich offer on e-commerce websites helps the users find what they need at one market place, the online catalogs are sometimes too overwhelming. Recommender systems play an important role in e-commerce websites as they improve the customer journey by helping the users find what they want at the right moment. These recommendations can be based on users’ characteristics, demographics, purchase or session history.In this thesis we focus on identifying complementary relationship between products in the case of the largest e-commerce company in the Netherlands. Complementary products are products that go well together, products that might be a necessity to the chosen product or simply a nice addition to it. At the company, there is big potential as complementary products increase the average purchase value and they exist for less than 20% of the whole catalog.We propose a content-based recommender system for detecting complemen- tary products, using a supervised deep learning approach that relies on Siamese Neural Network (SNN).The purpose of this thesis is three-fold; Firstly, the main goal is to create a SNN model that will be able to predict complementary products for any given product based on the content. For this purpose, we implement and compare two different models: Siamese Convolutional Neu- ral Network and Siamese Long Short-Term Memory (LSTM) Recurrent Neural Network. We feed these neural networks with pairs of products taken from the company, which are either complementary or non-complementary. Secondly, the basic assumption of our approach is that most of the important features for a product are included in its title, but we conduct experiments including the product description and brand as well. Lastly, we propose an extension of the SNN approach to handle millions of products in a matter of seconds.∼As a result from the experiments, we conclude that Siamese LSTM can predict complementary products with highest accuracy of 85%. Our assumption that the title is the most valuable attribute was confirmed. In addition, trans- forming our solution to a K-nearest-neighbour problem in order to optimize it for millions of products gave promising results.