Social bookmarking has gained popularity since the advent of Web 2.0. Keywords known as tags are created to annotate web content, and the resulting tag space composed of the tags, the resources, and the users arises as a new platform for web content discovery. Useful and interesting web resources can be located through searching and browsing based on tags, as well as following the user-user connections formed in the social bookmarking community. However, the effectiveness of tag-based search is limited due to the lack of explicitly represented semantics in the tag space. In addition, social connections between users are underused for web content discovery because of the inadequate social functions. In this research, we propose a comprehensive framework to reorganize the flat tag space into a hierarchical faceted model. We also studied the structure and properties of various networks emerging from the tag space for the purpose of more efficient web content discovery.The major research approach used in this research is social network analysis (SNA), together with methodologies employed in design science research. The contribution of our research includes: (i) a faceted model to categorize social bookmarking tags; (ii) a relationship ontology to represent the semantics of relationships between tags; (iii) heuristics to reorganize the flat tag space into a hierarchical faceted model using analysis of tag-tag co-occurrence networks; (iv) an implemented prototype system as proof-of-concept to validate the feasibility of the reorganization approach; (v) a set of evaluations of the social functions of the current networking features of social bookmarking and a series of recommendations as to how to improve the social functions to facilitate web content discovery.

Organizations are attempting to leverage their knowledge resources by integrating knowledge sharing systems, a key and new form of which are social computing tools. A large number of these initiatives fail, however, due to employees' reluctance to use, contribute content to, and share knowledge through such tools. Although research regarding one's motivation to share knowledge is extensive, there has been little research examining social computing systems, especially from the seeking and contributory perspectives—the two distinct, but closely interrelated facets of knowledge sharing. Motivated by such concerns, and by incorporating knowledge-seeking and knowledge- contribution perspectives in a single study, this research develops and empirically examines a theoretical model to explain what motivates employees to seek, contribute and share social tags using Enterprise Social Tagging Tools (ESTTs). Two research phases were employed to address the research objective. The goal of the first phase of the study was to explore factors affecting users’ tagging behavior in online social tagging tools. An extensive literature review was synthesized and a preliminary theoretical model emerged. A pilot study was conducted yielding 184 responses featuring eight different online social tagging tools. Mostly, the preliminary theoretical model showed positive influence on users’ tag behavior with a special focus on the newly developed concepts of information retrievability, information refindability. The goal of the study’s second phase was combining the results from the first phase with motivational theories to build and validate a belief-based and socio-organizational model that can explain employees’ tag seeking, contributing, and sharing behavior in ESTTs. The model was developed by employing theories such as Theory of Reasoned Action (TRA), Theory of Planned Behavior (TPB), Technology Acceptance Model (TAM), and social exchange theory. Through a large-scale survey (n=481) in two large Information Technology (IT) companies, the model was validated. The results speak to the importance of the three newly developed factors impacting employees’ tag seeking, contributing and sharing behavior. These factors are uniquely context-specific reflecting actual features of social tagging tools and potentially social media in general. Particularly, the results reveal that employees' tag seeking behavior is affected by their perception of the ESTTs in terms of enjoyment, information retrievability, ease of use, and managerial influence. In the context of tag contribution and sharing, the results show that employees contribute and share tags because of their perception of information refindability, ease of use, altruism, and pro-sharing norms. Differences among the seeking, contributing and sharing model have implications for future research and practice. / The thesis investigates employees' motivation to participate in enterprise social tagging tools. It describes and validates a conceputal model composed of three types of motivations: technical, social, and organizational.

Στη συγκεκριμένη Διπλωματική εργασία μελετώνται μέθοδοι κατασκευής συστήματος αναγνώρισης κακόβουλων - spammer χρηστών στο Διαδίκτυο. Συγκεκριμένα, επικεντρωνόμαστε στα Συστήματα Κοινωνικής Σελιδοσήμανσης, που αποτελούν έναν από τους βασικότερους τομείς σήμερα στο Διαδίκτυο. Οι μέθοδοι που χρησιμοποιούνται βασίζονται στο επιστημονικό πεδίο της Μηχανικής Μάθησης. Δοσμένου ενός πραγματικού συνόλου δεδομένων που περιγράφει έναν από τους πιο δημοφιλής Ιστότοπους Κοινωνικής Σελιδοσήμανσης, τον BibSonomy, εξάγονται χαρακτηριστικά σημασιολογικής φύσεως και εισάγονται σε ταξινομητές ώστε να διερευνηθεί η απόδοσή τους και να ευρεθούν οι βέλτιστες ρυθμίσεις τους στη διαδικασία ταυτοποίησης spammer και νόμιμων χρηστών. / In this Thesis are studied methods of designing a system that identifies malicious – spammer users on the Internet. In particular, we focus on Social Bookmarking Systems, which form one of the key areas on the Internet today. Methods are based on the scientific field of Machine Learning. Given a real dataset that describes one of the most popular Social Bookmarking website, BibSonomy, semantic features are extracted and introduced at classifiers in order to investigate the performance and determine the best settings in the process of identifying spammer and legitimate users.

This thesis is focused on using social applications from practical point of view in a real business environment. In fact, it is focused more on using them than dealing with hypothesis. There are two main objectives covering developing social application add-on and implementation of another type of social application in a company. The first objective is to develop social system, which provides functionality to fulfill team agenda for most of teams created within of scope on University of Economics. The second main objective is to describe important aspects of implementation Wiki system to one of departments in CSOB Company, the Bikipedia Project.

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Knowledge sharing–the dissemination of knowledge from an individual/group to another–has been an interesting topic for knowledge management scholars. Previous studies on knowledge sharing in online communities have primarily focused on communities of practice (organizational/business communities) and the social factors of knowledge sharing behaviour. However, non-business-oriented online communities have not been rigorously examined in the academic literature as venues for facilitating knowledge sharing. In addition, the burst of new age Internet tools (artifacts) such as social bookmarking has changed the face of online social networking. Within the context of Web 2.0, this socio-technical research investigation introduces both social and technical factors affecting attitude towards knowledge sharing in communities of relationship and communities of interest, and proposes a relational model of knowledge sharing attitude in Web 2.0 online communities. Social Capital Theory provides the main theoretical backbone for the proposed model. Theory of Reasoned Action (TRA) and social constructionsim have also been used. Following the description of the proposed hypotheses and research methodology using a survey about three Web 2.0 websites (Facebook, LinkedIn, and Cnet), data analysis through Partial Least Squared (PLS) method is applied to examine the effect of social and technical antecedent of knowledge sharing attitude. The R2 value of 0.78 indicates the strong explanatory power of the research model. / Dissertation / Doctor of Philosophy (PhD)

Nos travaux de recherche portent sur l'innovation et plus particulièrement sur le rôle de l'information dans la conception de produits. Le Web 2.0 repose sur la production de contenus par les internautes et constitue une source permanente et intarissable d'informations que les entreprises peuvent utiliser à des fins d'innovation, car si le Web a modifié les techniques de recherche d'informations et renforcé le travail de veille technologique, concurrentielle et commerciale, nous montrons que le Web 2.0 permet une meilleure connaissance des attentes et des besoins des consommateurs. Nous proposons l'analyse qualitative et quantitative des informations produites ou relayées par les internautes sous l'angle de leur pertinence au regard d'une démarche d'innovation. Nos expérimentations portent tout d'abord sur l'étude des Signets Sociaux (Social Bookmarking), nous montrons que l'exploration de ces annuaires thématiques co-constitués offre une alternative significative pour la recherche d'informations. Nous proposons une typologie des participants à cette plateforme afin de faciliter la détection d'usagers experts ou influents dans un domaine en particulier. Notre étude des commentaires sur le site de vente en ligne " Amazon.com ", montre que les clients participent de l'innovation incrémentale des entreprises en formulant des critiques pertinentes et constructives. Nous proposons alors une méthode d'extraction puis d'analyse de ces commentaires qui s'intègre aux dispositifs de veille an amont du projet d'innovation. Enfin, nous formulons les bases d'une méthode d'innovation qui consiste à mettre en place une observation permanente du Web 2.0 et dont l'objectif consiste à la production d'un document de référence destiné à orienter les innovations de l'entreprise : le " cahier des attentes ".

Web 2.0時代強調由使用者貢獻內容，並藉由使用者的互動來創造群體智慧的價值。社會性書籤網站統合散佈在各處的網路資訊（尤其是由使用者所產生的部落格文章），承接內容的生產及閱讀，是網路內容價值鏈樞紐；另一方面，從媒體的角度來看，書籤網站可視為是web 2.0下的公民新聞守門人（引路人），以公民取代專業編輯，提供了一個完全不一樣的公民媒體運作方式。本研究針對社會性書籤網站中的內容評價推薦機制，探討其群體智慧運作情形：參考動物群體行為的運作原則，加上文獻的整理及實際案例的觀察，建構出社會性書籤網站推薦機制的模擬運作架構；並透過代理人模擬方法，來找出影響網站群體智慧運作的原則，及相關屬性設定對運作結果的影響。研究結果發現，社會性書籤網站的運作成效，可以分為篩選效果及文章更新效率，兩者之間具有魚與熊掌不可兼得的特性，並可藉由不同的閱讀策略安排來調整。基於web 2.0的特性，使用者同時扮演服務的生產者與消費者。因此，使用者閱讀文章時的閱讀策略安排，可視為是群體智慧運作中的工作分配策略。而群體智慧的運作原則中，正回饋效應可以提升篩選效果，判斷獨立性可以提升文章的更新效率，抑制與負回饋則可以使系統較為穩定。本研究除了為web 2.0網站的群體智慧經營提供具體的參考方針，多重代理人模擬的方法也可做為往後web 2.0相關研究及網站經營時的工具。 / The core spirit for web 2.0 is the contribution of users, and the creation of value through the interaction between users. Social book marking sites integrate all kind of contents on the Internet (especially those generated by users), and play the role of pivot between content production and consumption. From the aspect of media, social bookmarking site can be regarded as news gatekeeper (or gateway) in the web 2.0 era. This study focuses on the rating and recommendation mechanism of social bookmarking sites, trying to find out the effects of collective wisdom with regard to different operations. The principle of collective animal behavior and the existing operations of some social bookmarking sites are first surveyed. Then, an operational model of social bookmarking sites and its recommendation mechanism is built and used for subsequent simulation. / The research findings show that the performance of social bookmarking sites has a tradeoff between sifting effect and efficiency, and that the performance can be controlled through a job allocation strategy. The operation of 「positive feedback」in collective wisdom can lead to sifting effect, 「integrity and variability」 leads to efficiency, and 「negative feedback」, 「inhibition」 lead to system stability. This research is believed to provide some managerial guidelines for web 2.0 sites operation.

Οι συνεχείς εξελίξεις στο χώρο του Διαδικτύου έχουν επιφέρει σημαντικές αλλαγές στο χώρο της εκπαιδευτικής τεχνολογίας. Καθοριστικό ρόλο προς αυτήν την κατεύθυνση έχει διαδραματίσει το Web 2.0, μια δεύτερη γενιά διαδικτυακών υπηρεσιών βασισμένων κατ' εξοχήν στη συμμετοχή του κοινού και τη συνεργασία των χρηστών. Τα τελευταία χρόνια πολλές από τις τεχνολογίες του Web 2.0 έχουν αρχίσει να αξιοποιούνται στο χώρο της εκπαίδευσης. Παρουσιάζεται μια εκτενής έρευνα σχετικά με τη χρήση εργαλείων στην εκπαίδευση και γίνεται μια προσπάθεια αξιολόγησης της συνεισφοράς τους στην εκπαιδευτική διαδικασία. Για την αποτίμηση της αποτελεσματικότητας και καταλληλότητας των εργαλείων στη εκπαίδευση, σχεδιάστηκε, υλοποιήθηκε και αξιολογήθηκε μια πιλοτική μελέτη στη Δευτεροβάθμια Εκπαίδευση. Επιλέχθηκε το μάθημα της Φυσικής για την Α' Λυκείου και μαθητές από το Πρότυπο Πειραματικό Λύκειο Πανεπιστημίου Πατρών. Συγκεκριμένα η μελέτη παρουσιάζει μια εφαρμογή εκπαιδευτικής πλατφόρμας, Ασύγχρονης Τηλεκπαίδευσης που δημιουργήθηκε για το σκοπό αυτό, αφού προστέθηκε στην γνωστή πλατφόρμα Open eClass από την GUnet το υποσύστημα Ιστολόγιο. Η εφαρμογή ονομάστηκε ePhysics και συνδυάζει εργαλεία όπως το Ιστολόγιο, το Σύστημα Wiki, οι Σύνδεσμοι, το Twiducate κ.α. Η εφαρμογή αυτή χρησιμοποιήθηκε στα πλαίσια μιας αυθεντικής εκπαιδευτικής δραστηριότητας για να υποστηρίξει τη συνεργασία των μαθητών. Τα αποτελέσματα της έρευνας έδειξαν πως στα πλαίσια μιας σωστής σχεδίασης, το ePhysics μπορεί να χρησιμοποιηθεί με επιτυχία για την υποστήριξη της συνεργασίας σε πραγματικές εκπαιδευτικές συνθήκες και να αποτελέσει μια ευέλικτη και αποδοτική μορφή συνεργατικής μάθησης στη Δευτεροβάθμια Εκπαίδευση. / The constant changes of the Internet have resulted in significant changes in educational technology. A decisive part towards this evolution is Web 2.0, a new generation of web services based on the principle of participation and collaboration of users. During the last years, many Web 2.0 technologies are utilised in various aspects of education. Moreover, we present a detailed study of the integration of Wiki-based tools in education and attempt to evaluate their contribution in the educational activity. For the assessment of the suitability and effectiveness of web 2.0 - tools in education, we have designed, implemented, and evaluated a pilot case study for Secondary Education. We have chosen the course of “Physics” for the A Grade of Lyceum and students from the Experimental Lyceum of the University of Patras. More specifically, the study presents an implementation of educational platform, Asynchronous eLearning that was designed for this purpose, after it was added in the also known platform Open eClass by GUnet the subsystem Blog. Our implementation was named ePhysics and it combines several tools such as Blog, Wikis, Links, Twiducate etc. This implementation was used in an authentic educational activity in order to support the collaboration between the students. The results of this study have proved that, under a correct design, ePhysics can be used with great success for supporting real educational activities and is a very flexible and efficient form of collaborative learning in Secondary Education.

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