exist on more than one network (i.e., multiplex links)?* Media multiplexity is a valuable source of tie strength information, and has further structural implications, which are of interest to OSN services and link prediction systems. We would like to explore the potential of identifying such links for building more successful online communities.\
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We will next present our multilayer framework for OSNs, and study user behaviour and properties across Twitter and Foursquare, extending our analysis to multiplex links in comparison with single-layer links. We finally integrate this into a link prediction system for OSNs, where we evaluate the utility of the metrics and features described in this work in hope to answer the above posed questions.

Multi-relational Framework
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The network of human interactions is usually represented by a graph $G$ where the nodes in set $V$ represent people and the edges $E$ represent interactions. While this representation has been immensely helpful for the uncovering of many social phenomena, it is focused on a single-layer abstraction of human relations. In this section, we describe a model, which represents the multiplexity of OSNs by supporting multiple friendship and interaction links.

Multilayer Online Social Network
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We represent the parallel interactions between 