Technological advances have led to the generation of large databases of organizational data recognized as an information-rich, strategic asset for internal analysis and sharing with trading partners. Data mining techniques can discover patterns in large databases including relationships considered strategically relevant to the owner of the data. The frequent item set hiding problem is an area of active research to study approaches for hiding the sensitive knowledge patterns before disclosing the data outside the organization. Several methods address hiding sensitive item sets including an exact approach that generates an extension to the original database that, when combined with the original database, limits the discovery of sensitive association rules without impacting other non-sensitive information. To generate the database extension, this method formulates a constraint optimization problem (COP). Solving the COP formulation is the dominant factor in the computational resource requirements of the exact approach. This dissertation developed heuristics that address the scalability of the exact hiding method. The heuristics are directed at improving the performance of COP solver by reducing the size of the COP formulation without significantly affecting the quality of the solutions generated. The first heuristic decomposes the COP formulation into multiple smaller problem instances that are processed separately by the COP solver to generate partial extensions of the database. The smaller database extensions are then combined to form a database extension that is close to the database extension generated with the original, larger COP formulation. The second heuristic evaluates the revised border used to formulate the COP and reduces the number of variables and constraints by selectively substituting multiple item sets with composite variables. Solving the COP with fewer variables and constraints reduces the computational cost of the processing. Results of heuristic processing were compared with an existing exact approach based on the size of the database extension, the ability to hide sensitive data, and the impact on nonsensitive data.

This thesis studies knowledge processes which span organisational boundaries, examining how knowledge is formed and shared between two companies with divergent interests, facing the challenges of innovation processes. Cross-boundary work provides access to diverse sources of knowledge, specialties and approaches, and this enhances the innovative performance of firms. However, managing knowledge and spanning diverse boundaries has proven to be difficult. While the epistemic and social challenges have been identified to trigger conflicts and misunderstandings across boundaries, the complexity, inter-dependency and uncertainty of innovation processes have been found to multiply these challenges. Informed by the practice-based perspective, this thesis examines how the challenges of integrating knowledge in such a context are addressed and resolved. Building upon this theoretical perspective, the thesis aims to enhance understandings of knowledge processes between the large bureaucratic organisations (publishers) and small/medium-sized companies (developers) in the videogames industry. Underpinned by a social constructionist and interpretivist methodology, a qualitative study of three publisher-developer relationships was conducted. With thirty six semi-structured interviews with senior directors, managers and team leaders, the thesis examined cross- boundary practices and the conflicts experienced in this process. In order to achieve this, the study focused on the role that boundary objects, trust development and power structures played in facilitating knowledge processes. The thesis recognises the evolving and relational character of boundary objects, highlighting that a combination of static and dynamic boundary objects were effective in facilitating knowledge integration in the publisher-developer relationship. It also reveals that despite high levels of distrust between the parties involved, they managed to create and maintain a working relationship by resorting to opportunistic practices, such as knowledge hiding, deception and collusion. It is emphasised that understanding the power dynamics in the publisher-developer relationship is a pre-requisite to explaining 2 how knowledge is managed across organisational boundaries during the course of a project. Drawing upon a Foucauldian perspective, the thesis identifies the positive and enabling aspects of power dynamics in this relationship. It argues that when the parties have discrepancies, competition and high levels of distrust, power games positively influence cross-boundary practices, the use of boundary objects and knowledge processes, ultimately mobilising knowledge integration. The thesis makes four significant contributions to the knowledge management and cross-boundary work literature. First, it identifies an evolving role for boundary objects, showing how they develop during the course of a project. Second, it finds a relational and politicised dimension for boundary objects, highlighting the role of brokers to manipulate and mobilise the use and effectiveness of these objects. Third, the thesis extends the existing literature by revealing that despite high levels of distrust, parties can create a working relationship. The research shows that this is achieved through resorting to opportunistic behaviour, such as knowledge hiding, deception and collusion. As a result, this thesis adds a complementary level to Carlile's Integrated Framework, explaining that when there are high levels of differences, dependencies and novelty in the cross-boundary work, knowledge hiding, deception and collusion are the driving force to facilitate knowledge integration and maintain a functional relationship. The fourth contribution of this thesis is recognising the positive and productive aspects of power dynamics that enable and mobilise boundary objects and knowledge processes, ultimately bringing positive outcomes and creating a functional relationship between two companies with divergent interests.

Aim: This study aims to explore the knowledge hiding phenomenon among project teammembers in the consulting industry. This study investigated why, when, how and what type ofknowledge team members hide.Methodology: This research applied a qualitative research with inductive approach. Semistructuredinterviews with eleven participants from EY in Kazakhstan were conducted.Secondary data was obtained from existing scientific articles and books.Findings: Findings of the study provided that (i) variables affecting knowledge hiding atindividual level also influence at team level; (ii) the technological and organizational barriershad a minor influence on knowledge hiding at team level; (ii) tacit/explicit and key/commonknowledge are subject to hiding among team members; (iv) three additional variables arediscovered at team level, i.e. laziness, fear of being seen silly and self-study. Theoretical contributions: This study contributes to the counterproductive knowledgebehaviour by exploring patterns of knowledge hiding among team members. Additionalknowledge sharing barriers of why and when team members hide knowledge were found. Teammembers hide knowledge when they feel ownership over knowledge and territoriality servesas a mediating tool. Nevertheless, collective knowledge psychological ownership weakensknowledge hiding, because team’s success is more important than individual’s goals.Managerial implications: Organizations are encouraged to nurture team environment, becauseteam members might feel that they are obliged to share their knowledge. Also, managementshould consider to lower territoriality perspectives (e.g. by team buildings, etc.). Limitations and future research: Future research should increase the number of respondentsfrom different companies, industries and geographical areas. To validate the three newly foundknowledge hiding variables at team level, they can be tested at individual level. On top of thatfuture research can focus on the effects of interpersonal injustice on knowledge hiding on eachmember, motivational process on knowledge concealing/sharing and cross-cultural differencesof how knowledge concealing is interpreted can be researched.

The effects of goal interdependence on employees’ performance outcomes have been well documented in the literature. Yet, the relationship between goal interdependence and employees’ proactive behaviors remains largely unexplored. Integrating the theory of cooperation and competition with the employee proactivity literature, this study investigates how cooperative goal interdependence and competitive goal interdependence respectively influence employee knowledge sharing and knowledge hiding, and in turn shape their propensity to seek help from coworkers. It further examines reciprocity beliefs as an individual factor in affecting the indirect effect of goal interdependence on help seeking. Specifically, positive reciprocity belief is hypothesized to moderate the mediating role of knowledge sharing, whereas negative reciprocity belief is expected to moderate the mediating effect of knowledge hiding. In Study 1, a total of 127 interviews were conducted with full-time employees working in professional service firms across four cities including Hong Kong, Macau, China and Taiwan. Results of structural equation modeling supported the mediating role of knowledge sharing in the relationship between cooperative goal interdependence and employee help seeking. In Study 2, an experimental study was conducted with 150 full-time students at a university in Macau to replicate the findings in Study 1 and to test the moderation hypotheses. It yielded findings consistent with Study 1 and supportive of the moderating role of negative reciprocity belief in the mediated effect of goal interdependence on help seeking. Specifically, knowledge hiding mediates the relationship between competitive goal interdependence and help seeking, when an individual is high in negative reciprocity belief. Findings of the two studies provide both theoretical contributions to the literature and practical insights to organizations. Cooperative goal interdependence is a valuable method for managers to promote knowledge sharing, inhibit knowledge hiding, and encourage active help seeking among employees.

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Advances in data collection and data storage technologies have given way to the establishment of transactional databases among companies and organizations, as they allow enormous volumes of data to be stored efficiently. Most of the times, these vast amounts of data cannot be used as they are. A data processing should first take place, so as to extract the useful knowledge. After the useful knowledge is mined, it can be used in several ways depending on the nature of the data. Quite often, companies and organizations are willing to share data for the sake of mutual benefit. However, these benefits come with several risks, as problems with privacy might arise, as a result of this sharing. Sensitive data, along with sensitive knowledge inferred from these data, must be protected from unintentional exposure to unauthorized parties. One form of the inferred knowledge is frequent patterns, which are discovered during the process of mining the frequent itemsets from transactional databases. The problem of protecting such patterns is known as the frequent itemset hiding problem. In this thesis, we review several techniques for protecting sensitive frequent patterns in the form of frequent itemsets. After presenting a wide variety of techniques in detail, we propose a novel approach towards solving this problem. The proposed method is an approach that combines heuristics with linear-programming. We evaluate the proposed method on real datasets. For the evaluation, a number of performance metrics are presented. Finally, we compare the results of the newly proposed method with those of other state-of-the-art approaches. / Η ραγδαία εξέλιξη των τεχνολογιών συλλογής και αποθήκευσης δεδομένων οδήγησε στην καθιέρωση των βάσεων δεδομένων συναλλαγών σε οργανισμούς και εταιρείες, καθώς επιτρέπουν την αποδοτική αποθήκευση τεράστιου όγκου δεδομένων. Τις περισσότερες φορές όμως, αυτός ο τεράστιος όγκος δεδομένων δεν μπορεί να χρησιμοποιηθεί ως έχει. Μια πρώτη επεξεργασία των δεδομένων πρέπει να γίνει, ώστε να εξαχθεί η χρήσιμη πληροφορία. Ανάλογα με τη φύση των δεδομένων, αυτή η χρήσιμη πληροφορία μπορεί να χρησιμοποιηθεί στη συνέχεια αναλόγως. Αρκετά συχνά, οι εταιρείες και οι οργανισμοί είναι πρόθυμοι να μοιραστούν τα δεδομένα μεταξύ τους με στόχο το κοινό τους όφελος. Ωστόσο, αυτά τα οφέλη συνοδεύονται με διάφορους κινδύνους, καθώς ενδέχεται να προκύψουν προβλήματα ιδιωτικής φύσης, ως αποτέλεσμα αυτής της κοινής χρήσης των δεδομένων. Ευαίσθητα δεδομένα, μαζί με την ευαίσθητη γνώση που μπορεί να προκύψει από αυτά, πρέπει να προστατευτούν από την ακούσια έκθεση σε μη εξουσιοδοτημένους τρίτους. Μια μορφή της εξαχθείσας γνώσης είναι τα συχνά μοτίβα, που ανακαλύφθηκαν κατά την εξόρυξη συχνών στοιχειοσυνόλων από βάσεις δεδομένων συναλλαγών. Το πρόβλημα της προστασίας συχνών μοτίβων τέτοιας μορφής είναι γνωστό ως το πρόβλημα απόκρυψης συχνών στοιχειοσυνόλων. Στην παρούσα διπλωματική εργασία, εξετάζουμε διάφορες τεχνικές για την προστασία ευαίσθητων συχνών μοτίβων, υπό τη μορφή συχνών στοιχειοσυνόλων. Αφού παρουσιάσουμε λεπτομερώς μια ευρεία ποικιλία τεχνικών απόκρυψης, προτείνουμε μια νέα προσέγγιση για την επίλυση αυτού του προβλήματος. Η προτεινόμενη μέθοδος είναι μια προσέγγιση που συνδυάζει ευρετικές μεθόδους με γραμμικό προγραμματισμό. Για την αξιολόγηση της προτεινόμενης μεθόδου χρησιμοποιούμε πραγματικά δεδομένα. Για τον σκοπό αυτό, παρουσιάζουμε επίσης και μια σειρά από μετρικές αξιολόγησης. Τέλος, συγκρίνουμε τα αποτελέσματα της νέας προτεινόμενης μεθόδου με άλλες κορυφαίες προσεγγίσεις.