The advances in social media and social computing technologies have dramatically changed the way through which people interact, organize, and collaborate. The use of social media also makes the large-scale data revealing human behavior accessible to researchers and practitioners. The analysis and modeling of social networks formed from relatively stable online communities have been extensively studied. The research on the structural and dynamical patterns of large-scale crowds motivated by accomplishing common goals, named the cyber movement organizations (CMO) or cyber-enabled social movement organizations (CeSMO), however, is still limited to anecdotal case studies. This research is one of the first steps towards the understanding of the CMO/CeSMO based on real data collected from online social media.The focus of my research is on the study of an important type of CMO/CeSMO, the crowd-powered search behavior (also known as human flesh search, HFS), in which a large number of Web users voluntarily gathered together to find out the truth of an event or the information of a person that could not be identified by one single person or simple online searches. In this research, I have collected a comprehensive data-set of HFS. I first introduce the phenomenon of HFS and reviewed the study of online social groups/communities. Then, I present the empirical studies of both individual HFS episodes and aggregated HFS communities, and unveiled their unique topological properties. Based on the empirical findings, I propose two models to simulate evolution and topology of individual HFS networks. I conclude the dissertation with discussions of future research of CMO/CeSMO.

<p>When computational systems become increasingly mobile and ubiquitous, digital information and the use of computational systems may increasingly be immersed into the physical and social world of objects, people and practices. However, the digital, physical and social materials that make up these hybrid spaces have different characteristics and are hard to understand for users. In addition, users are themselves part in constructing and re-constructing the hybrid spaces.</p><p>The main question addressed in this thesis is whether making aspects of the digitally mediated hybrid spaces observable and accessible provides support to users. The observability may provide support for the specific task at hand or help in building an understanding for what the system does and how, an understanding that is needed to explain system output and to cope with service breakdowns. The fundament of the approach is to empower users of computational systems to actively make sense of the system themselves.</p><p>Two prototype services are described, Socifer and MobiTip. Their common denominator was to make digitally mediated parts of the hybrid spaces observable to users. Without disqualifying other kinds of information, the work focussed on digitally mediated social trails of other users.</p><p>Building on experience from the prototype work and an investigation into in seamful design, observability and awareness, I have investigated the effects of making a computational system’s social context observable to users in a way that</p><p>- is separated from the service’s main functionality in the interface, allowing it to become peripheral and non-obtrusive;</p><p>- uses simple models and little interpretation;</p><p>- to some extent opens up the service to allow for user appropriation of both service content and functionality; and</p><p>- is informative rather than proactive in order to empower the user rather than acting on the user’s behalf.</p><p>By designing systems that fulfil these criteria I claim that the user will be supported in performing the task at hand, with or without the service, and that with service use, the user will become more and more aware of the possibilities and limitations of the underlying technology. In addition, the digitally mediated hybrid spaces where physical, social and digital contexts meet constitute application domains in themselves, domains that users may enjoy exploring.</p>

When computational systems become increasingly mobile and ubiquitous, digital information and the use of computational systems may increasingly be immersed into the physical and social world of objects, people and practices. However, the digital, physical and social materials that make up these hybrid spaces have different characteristics and are hard to understand for users. In addition, users are themselves part in constructing and re-constructing the hybrid spaces. The main question addressed in this thesis is whether making aspects of the digitally mediated hybrid spaces observable and accessible provides support to users. The observability may provide support for the specific task at hand or help in building an understanding for what the system does and how, an understanding that is needed to explain system output and to cope with service breakdowns. The fundament of the approach is to empower users of computational systems to actively make sense of the system themselves. Two prototype services are described, Socifer and MobiTip. Their common denominator was to make digitally mediated parts of the hybrid spaces observable to users. Without disqualifying other kinds of information, the work focussed on digitally mediated social trails of other users. Building on experience from the prototype work and an investigation into in seamful design, observability and awareness, I have investigated the effects of making a computational system’s social context observable to users in a way that - is separated from the service’s main functionality in the interface, allowing it to become peripheral and non-obtrusive; - uses simple models and little interpretation; - to some extent opens up the service to allow for user appropriation of both service content and functionality; and - is informative rather than proactive in order to empower the user rather than acting on the user’s behalf. By designing systems that fulfil these criteria I claim that the user will be supported in performing the task at hand, with or without the service, and that with service use, the user will become more and more aware of the possibilities and limitations of the underlying technology. In addition, the digitally mediated hybrid spaces where physical, social and digital contexts meet constitute application domains in themselves, domains that users may enjoy exploring.

Consumers face several challenges using the Internet to fill health-related needs. (1) In many cases, they face a language gap as they look for information that is written in unfamiliar technical language. (2) Medical information in social media is of variable quality and may be appealing even when it is dangerous. (3) Discussion groups provide valuable social support for necessary lifestyle changes, but are variable in their levels of activity. (4) Finding less popular groups is tedious. We present solutions to these challenges. We use a novel adaptation of topic models to address the language gap. Conventional topic models discover a set of unrelated topics that together explain the combinations of words in a collection of documents. We add additional structure that provides relationships between topics corresponding to relationships between consumer and technical medical topics. This allows us to support search for technical information using informal consumer medical questions. We also analyze social media related to eating disorders. A third of these videos promote eating disorders and consumers are twice as engaged by these dangerous videos. We study the interactions of two communities in a photo-sharing site. There, a community that encourages recovery from eating disorders interacts with the pro-eating disorder community in an attempt to persuade them, but we found that this attempt entrenches the pro-eating disorder community more firmly in its position. We study the process by which consumers participate in discussion groups in an online diabetes community. We develop novel event history analysis techniques to identify the characteristics of groups in a diabetes community that are correlated with consumer activity. This analysis reveals that uniformly advertise the popular groups to all consumers impairs the diversity of the groups and limits their value to the community. To help consumers find interesting discussion groups, we develop a system for personalized recommendation for social connections. We extend matrix factorization techniques that are effective for product recommendation so that they become suitable for implicit power-law-distributed social ratings. We identify the best approaches for recommendation of a variety of social connections involving consumers, discussion groups and discussions.

Οι εφαρμογές συναίσθησης (awareness applications) αποτελούν συστήματα ενίσχυσης της αντίληψης της παρουσίας (presence) και εντάσσονται στην ευρύτερη κατηγορία των συστημάτων υποστήριξης της επικοινωνίας με τη διαμεσολάβηση υπολογιστών (computer mediated communication systems). Μια πληθώρα τέτοιων εφαρμογών – μικρών και εξειδικευμένων ακόμη – έχει αναπτυχθεί τα τελευταία χρόνια (π.χ. MSN, Facebook), ενώ αναμένεται η ευρύτερη διάδοσή τους ως αποτέλεσμα της ανάπτυξης των κινητών επικοινωνιών. Η παρούσα διπλωματική εργασία βασίζεται στην πλατφόρμα ανάπτυξης εφαρμογών συναίσθησης ASTRA. Το συγκριτικό πλεονέκτημα της πλατφόρμας απέναντι στις υπάρχουσες εφαρμογές είναι ότι είναι γενικευμένη και συνεπώς μπορεί να οδηγήσει στην ανάπτυξη πλήθους εφαρμογών με σχετικά εύκολο τρόπο, δίνοντας τεράστια ώθηση στην ευρύτερη ανάπτυξη του πεδίου. Η εργασία αποσκοπεί στην δημιουργία ενός πλαισίου αξιολόγησης (evaluation framework) εφαρμογών συναίσθησης, το οποίο θα βασίζεται κυρίως στο πρότυπο ISO 9126. Για το σκοπό αυτό θα αναλυθεί το εν λόγω πρότυπο και θα εντοπιστούν οι ιδιαίτερες διαστάσεις των συστημάτων συναίσθησης (τα οποία θα αναλυθούν ως εφαρμογές διαδικτύου). Στη συνέχεια θα ομαδοποιηθούν τα χαρακτηριστικά τους και θα ενταχθούν στα τέσσερα στοιχεία εξωτερικής ποιότητας που προβλέπει το πρότυπο. Ως πεδίο εφαρμογής του πλαισίου θα χρησιμοποιηθεί η πλατφόρμα ASTRA, η οποία θα αξιολογηθεί με βάση αυτό. Για το σκοπό της εργασίας θα αναπτυχθούν και ορισμένες εφαρμογές συναίσθησης με τη χρήση της πλατφόρμας. / This thesis presents a quality evaluation framework for awareness systems. These are Computer Mediated Communication (CMC) systems, which support people’s needs to communicate and enhance their sense of presence. In general, quality is defined by the extent to which the software meets user needs and requirements. Our framework is based on the ISO9126 standard, which includes two quality dimensions, external and internal, and defines a set of quality criteria for each. We have chosen to adopt the end-user standpoint in evaluating awareness systems, thus we model only the four criteria groups of external quality, that is, functionality, usability, reliability and efficiency. Firstly, we present a brief introduction to software quality and the ISO9126 standard. Then, we present presence and awareness systems, and discuss their emergence and the needs they serve. We continue with a broad survey of presence and awareness systems and social software. For each of the surveyed systems (the list includes Facebook, MSN, Twitter, YouTube, LinkedIn et al), we present an extensive list of features, which support user/community management and application management. A comparative table summarizes the features of the systems surveyed. Based on this discussion, we develop the proposed evaluation framework, by listing detailed criteria for each of the four groups of external quality, according to ISO9126. For each group, we list two tables of criteria, one for community management evaluation and one for application evaluation. The criteria are sub-grouped into presentation, navigation, escalation, content, applications, communication, awareness, and connectedness. Each table is followed by a brief explanation of the criteria it contains and the range of values they assume. Then we present in detail ASTRA, the first pervasive CMC system that was designed and developed in order to enhance presence without requiring users to use a computer to join. ASTRA applies a pervasive computing interface on top of a social computing system, which supports community and awareness application management. The focus-nimbus model is used to describe the awareness framework and a novel connectedness theory is validated with the system. Finally, we evaluate and classify the presence and awareness systems, including ASTRA, according to the proposed evaluation framework.

Software development has become a cognitive and collaborative knowledge-based endeavor where developers and organizations, faced with a variety of challenges and an increased demand for extensive knowledge support, push the boundaries of existing tools and work practices. Researchers and industry professionals have spent years studying collaborative work and communication media, however, the landscape of social media is rapidly changing. Thus, instead of trying to model the use of specific technologies and communication media, I seek to model the knowledge-building process itself. Doing so will not only allow us to understand specific tool and communication media use, but whole ecosystems of technologies and their impact on software development and knowledge work, revealing aspects not only unique to specific tools, but also aspects about the combination of technologies. In this dissertation, I describe the empirical studies I conducted aimed to understand social and communication media use in software development and knowledge curation within developer communities. An important part of the thesis is an additional qualitative meta-synthesis of these studies. My meta-analysis has led to a model of software development as a knowledge building process, and a theoretical framework: I describe this newly formed framework and how it is grounded in empirical work, and demonstrate how my primary studies led to its creation. My conceptualization of knowledge building withing software development and the proposed framework provide the research community with the means to pursue a deeper understanding of software development and contemporary knowledge work. I believe that this framework can serve as a basis for a theory of knowledge building in software development, shedding light on knowledge flow, knowledge productivity, and knowledge management. / Graduate

abstract: In most social networking websites, users are allowed to perform interactive activities. One of the fundamental features that these sites provide is to connecting with users of their kind. On one hand, this activity makes online connections visible and tangible; on the other hand, it enables the exploration of our connections and the expansion of our social networks easier. The aggregation of people who share common interests forms social groups, which are fundamental parts of our social lives. Social behavioral analysis at a group level is an active research area and attracts many interests from the industry. Challenges of my work mainly arise from the scale and complexity of user generated behavioral data. The multiple types of interactions, highly dynamic nature of social networking and the volatile user behavior suggest that these data are complex and big in general. Effective and efficient approaches are required to analyze and interpret such data. My work provide effective channels to help connect the like-minded and, furthermore, understand user behavior at a group level. The contributions of this dissertation are in threefold: (1) proposing novel representation of collective tagging knowledge via tag networks; (2) proposing the new information spreader identification problem in egocentric soical networks; (3) defining group profiling as a systematic approach to understanding social groups. In sum, the research proposes novel concepts and approaches for connecting the like-minded, enables the understanding of user groups, and exposes interesting research opportunities. / Dissertation/Thesis / Ph.D. Computer Science 2013

abstract: The rapid advancements of technology have greatly extended the ubiquitous nature of smartphones acting as a gateway to numerous social media applications. This brings an immense convenience to the users of these applications wishing to stay connected to other individuals through sharing their statuses, posting their opinions, experiences, suggestions, etc on online social networks (OSNs). Exploring and analyzing this data has a great potential to enable deep and fine-grained insights into the behavior, emotions, and language of individuals in a society. This proposed dissertation focuses on utilizing these online social footprints to research two main threads – 1) Analysis: to study the behavior of individuals online (content analysis) and 2) Synthesis: to build models that influence the behavior of individuals offline (incomplete action models for decision-making). A large percentage of posts shared online are in an unrestricted natural language format that is meant for human consumption. One of the demanding problems in this context is to leverage and develop approaches to automatically extract important insights from this incessant massive data pool. Efforts in this direction emphasize mining or extracting the wealth of latent information in the data from multiple OSNs independently. The first thread of this dissertation focuses on analytics to investigate the differentiated content-sharing behavior of individuals. The second thread of this dissertation attempts to build decision-making systems using social media data. The results of the proposed dissertation emphasize the importance of considering multiple data types while interpreting the content shared on OSNs. They highlight the unique ways in which the data and the extracted patterns from text-based platforms or visual-based platforms complement and contrast in terms of their content. The proposed research demonstrated that, in many ways, the results obtained by focusing on either only text or only visual elements of content shared online could lead to biased insights. On the other hand, it also shows the power of a sequential set of patterns that have some sort of precedence relationships and collaboration between humans and automated planners. / Dissertation/Thesis / Doctoral Dissertation Computer Science 2019

Depuis quelques années, des évolutions importantes ont lieu en matière d’infrastructures technologiques. En particulier, la démocratisation des dispositifs mobiles (comme les PCs, Smartphones, Tablettes, etc.) a rendu l’information accessible par le grand public partout et à tout moment, ce qui est l’origine du concept d’informatique ubiquitaire. L’approche classique des systèmes de l’informatique ubiquitaire, qui répondent aux besoins des utilisateurs indépendants les uns des autres, a été bouleversée par l’introduction de la dimension sociale. Ce rapprochement est à l’origine d’une discipline naissante « le pervasive social computing » ou l’informatique socio-pervasive. Les applications socio-pervasives connaissent une véritable expansion. Ces dernières intègrent de plus en plus la notion de communauté. Le succès des applications communautaires se justifie par le but poursuivi par ces dernières qui est de répondre aux besoins des communautés et d’offrir un ‘chez soi’ virtuel, spécifique à la communauté, dans lequel elle va construire sa propre identité et réaliser ses objectifs. Par ailleurs, la notion de communauté représente une source d’informations contextuelles sociales. Elle est, aujourd’hui, au cœur des problématiques de personnalisation et d’adaptation des applications informatiques. Dans le cadre de cette thèse, nous étudions sous différents aspects les applications informatiques centrées communautés existantes et soulignons un certain nombre de carences au niveau même de la notion de communauté, des modèles de communautés, ou encore des architectures dédiées à ces applications communautaires, etc. Pour remédier à ces défauts, nous proposons trois principales contributions : Un nouveau type de communauté adapté aux exigences des environnements pervasifs qui vient rompre avec les traditionnelles communautés pérennes thématiques : des communautés éphémères, géolocalisées et spontanées (sans contrainte thématique). 
 Un modèle de communauté basé sur les standards du web sémantique pour répondre aux problèmes liés à l’hétérogénéité de conception des communautés. Une architecture dynamiquement reconfigurable pour promouvoir les communautés spontanées en aidant les utilisateurs nomades à intégrer des communautés environnantes et à découvrir les services dédiés. 
Nous montrons la faisabilité de nos propositions pour la conception et le développement d’applications communautaires spontanées grâce au prototype Taldea. Enfin, nous testons les approches proposées de découverte de communauté et de services à travers plusieurs scénarios caractérisés par la mobilité et l’ubiquité. / Advances in technology, in particular the democratization of mobile devices (PCs, smartphones and tablets), has made information accessible to anyone at any time and from anywhere while facilitating the capture of physical contextual data, thereby justifying the growing interest for pervasive computing. The classical approach of pervasive computing has been affected by the introduction of the social dimension. Ubiquitous systems do not meet the needs of users independently from each other but do take into account their social context. Fostering the social dimension has given rise to a fast growing research field called Pervasive Social Computing. Applications in this area are increasingly concerned by communities. The contextual information associated with a community can be harnessed for personalization, adaptability and dynamic deployment of services, which are important factors for Pervasive Computing. A community is considered in our approach as a set of distinct social entities that should be supported with services as a single user is. In this thesis, we look into different aspects of existing centered communities applications and we identify several weaknesses and shortcomings in the notion of community, the community models, and the architecture of communities’ applications. To overcome these shortcomings, we propose three main contributions: A new type of communities that fits better with the requirements of pervasive environments: short- lived, geolocated and spontaneous (without thematic constraint) community. Intuitively, it is the type of community that best matches with circumstantial, accidental, incidental or fortuitous situations. This kind of community has to meet specific needs, which are not taken into account by perennial thematic communities. 
 A model for communities based on semantic web standards to overcome the problem of heterogeneity across definitions and models. The ontological representation allows us to organize and represent social data, to make information searches easier for users and to infer new knowledge. 
 A dynamically reconfigurable architecture for fostering spontaneous communities in order to facilitate the user access to communities, information exchange between community members and service discovery. 
The proposed architecture for community and service discovery have been validated through a prototype called Taldea and have been tested through several scenarios characterized by mobility and ubiquity.

This dissertation investigates ways of supporting parents in managing youth's social media use. I present empirical evidence of the challenges parents face in managing youth technology use. I then translate these results into the design and deployment of ParentNet, a community-based online social network for middle school parents to keep up with changes in technology. This dissertation provides new insights into the opportunities and challenges in conducting HCC research with a particular demographic, parents and youth. The contributions of this research are: (1) empirical studies of challenges parents face in managing youth technology use; (2) the design and deployment of a community-based online social network called ParentNet; (3) limitations and design considerations for deploying technological interventions for different social groups; and (4) reflection on emerging themes around overuse and disconnection in daily life.