Kant, Krishna; Shi, Justin Y.; Tan, Chiu C.; Biswas, Saroj K. (Temple University. Libraries, 2018)
      Cloud computing has brought availability of services at unprecedented scales but data accessibility considerations become more complex due to involvement of multiple parties in providing the infrastructure. In this thesis, we discuss the problem of enabling cooperative data access in a multi-cloud environment where the data is owned and managed by multiple enterprises. We consider a multi-party collaboration scheme whereby a set of parties collectively decide accessibility to data from individual parties using different data models such as relational databases, and graph databases. In order to implement desired business services, parties need to share a selected portion of information with one another. We consider a model with a set of authorization rules over the joins of basic relations, and such rules are defined by these cooperating parties. The accessible information is constrained by these rules. Specifically, the following critical issues were examined: Combine rule enforcement and query planning and devise an algorithm which simultaneously checks for the enforceability of each rule and generation of minimum cost plan of its execution using a cost metric whenever the enforcement is possible; We also consider other forms of limiting the access to the shared data using safety properties and selection conditions. We proposed algorithms for both forms to remove any conflicts or violations between the limited accesses and model queries; Used graph databases with our authorization rules and query planning model to conduct similarity search between tuples, where we represent the relational database tuples as a graph with weighted edges, which enables queries involving "similarity" across the tuples. We proposed an algorithm to exploit the correlations between attributes to create virtual attributes that can be used to catch much of the data variance, and enhance the speed at which similarity search occurs; Proposed a framework for defining test functionalities their composition, and their access control. We discussed an algorithm to determine the realization of the given test via valid compositions of individual functionalities in a way to minimize the number of parties involved. The research significance resides in solving real-world issues that arise in using cloud services for enterprises After extensive evaluations, results revealed: collaborative data access model improves the security during cooperative data processes; systematic and efficient solving access rules conflict issues minimizes the possible data leakage; and, a systematic approach tackling control failure diagnosis helps reducing troubleshooting times and all that improve availability and resiliency. The study contributes to the knowledge, literature, and practice. This research opens up the space for further studies in various aspects of secure data cooperation in large-scale cyber and cyber-physical infrastructures.