Egocentric online social networks: Analysis of key features and prediction of tie strength in Facebook

The widespread use of online social networks, such as Facebook and Twitter, is generating a growing amount of accessible data concerning social relationships. The aim of this work is twofold. First, we present a detailed analysis of a real Facebook data set aimed at characterising the properties of human social relationships in online environments. We find that certain properties of online social networks appear to be similar to those found ?offline? (i.e., on human social networks maintained without the use of social networking sites). Our experimental results indicate that on Facebook there is a limited number of social relationships an individual can actively maintain and this number is close to the well-known Dunbar?s number (150) found in offline social networks. Second, we also present a number of linear models that predict tie strength (the key figure to quantitatively represent the importance of social relationships) from a reduced set of observable Facebook variables. Specifically, we are able to predict with good accuracy (i.e., higher than 80%) the strength of social ties by exploiting only four variables describing different aspects of users interaction on Facebook. We find that the recency of contact between individuals ? used in other studies as the unique estimator of tie strength ? has the highest relevance in the prediction of tie strength. Nevertheless, using it in combination with other observable quantities, such as indices about the social similarity between people, can lead to more accurate prediction

Models of Social Networking and Information Diffusion in Future Internet Cyber-Physical Environments

Negli ultimi anni, la grande diffusione di tecnologie ICT, es. dispositivi mobili e servizi di social networking, hanno portato alla proliferazione di reti elettroniche e comunità virtuali in cui i contenuti sono generati e propagati dagli utenti ICT. Poiché gli utenti interagiscono anche nel mondo fisico tramite relazioni sociali umane, le informazioni generate nel mondo virtuale possono produrre effetti nel mondo fisico e vice versa. Questo fenomeno, chiamato cyber-physical convergence, sta diventando un argomento di ricerca di rilievo per la progettazione e test di servizi avanzati di social networking. In questa tesi vengono forniti nuovi fondamentali spunti riguardo la cyber-physical convergence, verificando che le proprietà delle reti sociali umane, formate nel mondo fisico, possono essere mappate direttamente sulle strutture sociali formate dagli utenti ICT nel mondo virtuale. Questo risultato ci permette di definire una nuova generazione di modelli di rete vengono catturate le caratteristiche chiave delle relazioni sociali umane sia del mondo virtuale che di quello fisico. Dato che le relazioni sociali sono una delle basi della comunicazione e degli schemi di scambio di informazioni tra utenti, questi modelli sono strumenti utili per progettare e valutare le performance di soluzioni tecniche content-centric per scenari in cui si verifica la cyber-physical convergence. Un altro contributo di questa tesi, per la progettazione di servizi content-centric, è la definizione e la valutazione di nuove modelli di information diffusion. I nostri modelli sono in grado di riprodurre fedelmente i tipici schemi di diffusione delle OSNs, e che possono essere usati per studiare "in vitro" le performance dei servizi di information diffusion rispetto ai parametri chiave del sistema e del comportamento degli utenti. In the last years, the large diffusion of ICT technologies, e.g. personal devices and social networking services, led to the proliferation of electronic networks and virtual communities in which new content is generated and propagated by ICT users. Since users also interact in the physical world through human social relationships, the information generated in the cyber world can produce outcomes in the physical world and vice-versa. This phenomenon, called cyber-physical convergence, is becoming a prominent topic of research for the design of efficient Future Internet solutions. Indeed, such integration can be exploited for the design of efficient networking solutions for content dissemination and for the development and testing of advanced social networking services. In this thesis we provide new fundamental insights about the cyber-physical convergence, verifying that the properties of the human social networks, formed in the physical world, can be directly mapped to the social structures formed by ICT users in the cyber world. This result allows us to define a new generation of network models where we capture the key characteristics of human social relationships both in the cyber and in the physical worlds. As social relationships are one of the basis of communication and information exchange patterns between users, these models are useful tools to design and evaluate the performance of content-centric technical solutions for cyber-physical converging scenarios. Another contribution of this thesis, towards the design of content-centric services, is the definition and evaluation of novel information dissemination models. Our models are able to closely re-produce typical information diffusion patterns in OSNs, and can be used to understand "in vitro" the performance of information diffusion services with respect to key parameters of the system and users' behaviour