Over the last decade, we have witnessed an explosion in cloud services for hosting software applications (Software-as-a-Service), for building distributed services (Platform- as-a-Service), and for providing general computing infrastructure (Infrastructure-as-a- Service). Today, most cloud services are programmatically accessed through Application Programming Interfaces (APIs) that follow the REpresentational State Trans- fer (REST) software architectural style and cloud service developers use interface-description languages to describe and document their services. My thesis is that we can leverage the structured usage of cloud services through REST APIs and feedback obtained during interaction with such services in order to build systems that test cloud services in an automatic, efficient, and learning-based way through their APIs. In this dissertation, I introduce stateful REST API fuzzing and describe its implementation in RESTler: the first stateful REST API fuzzing system. Stateful means that RESTler attempts to explore latent service states that are reachable only with sequences of multiple interdependent API requests. I then describe how stateful REST API fuzzing can be extended with active property checkers that test for violations of desirable REST API security properties. Finally, I introduce Pythia, a new fuzzing system that augments stateful REST API fuzzing with coverage-guided feedback and learning-based mutations.

Nested virtualization, the discipline of running virtual machines inside other virtual machines, is increasingly important because of the need to deploy workloads that are already using virtualization on top of virtualized cloud infrastructures. However, nested virtualization performance on modern computer architectures is far from native execution speed, which remains a key impediment to further adoption. My thesis is that simple changes to hardware, software, and virtual machine configuration that are transparent to nested virtual machines can provide near-native execution speed for real application workloads. This dissertation presents three mechanisms that improve nested virtualization performance. First, we present NEsted Virtualization Extensions for Arm (NEVE). As Arm servers make inroads in cloud infrastructure deployments, supporting nested virtualization on Arm is a key requirement. The requirement has recently been met with the introduction of nested virtualization support for the Arm architecture. We built the first hypervisor using Arm nested virtualization support and show that, despite similarities between Arm and x86 nested virtualization support, performance on Arm is much worse than on x86. This is due to excessive traps to the hypervisor caused by differences in non-nested virtualization support. To address this problem, we introduce a novel paravirtualization technique to rapidly prototype architectural changes for virtualization and evaluate their performance impact using existing hardware. Using this technique, we introduce NEVE, a set of simple architectural changes to Arm that can be used by software to coalesce and defer traps by logging the results of hypervisor instructions until the results are actually needed by the hypervisor. We show that NEVE allows hypervisors running real application workloads to provide an order of magnitude improvement in performance over current Arm nested virtualization support and up to three times less overhead than x86 nested virtualization. NEVE is included in the Armv8.4 architecture. Second, we introduce virtual-passthrough, a new approach for providing virtual I/O devices for nested virtualization without the intervention of multiple levels of hypervisors. Virtual-passthrough preserves I/O interposition while addressing the performance problem of I/O intensive workloads as they perform many times worse with nested virtualization than without virtualization. With virtual-passthrough, virtual devices provided by a host hypervisor, the hypervisor that runs directly on the hardware, can be assigned to nested virtual machines directly without delivering data and control through multiple layers of hypervisors. The approach leverages the existing direct device assignment mechanism and implementation, so it only requires virtual machine configuration changes. Virtual-passthrough is platform-agnostic and easily supports important virtualization features such as migration. We have applied virtual-passthrough in the Linux KVM hypervisor for both x86 and Arm hardware, and show that it can provide more than an order of magnitude improvement in performance over current KVM virtual device support on real application workloads. Third, we introduce Direct Virtual Hardware (DVH), a new approach that enables a host hypervisor to directly provide virtual hardware to nested virtual machines without the intervention of multiple levels of hypervisors. DVH is a generalization of virtual-passthrough and does not limit virtual hardware to I/O devices. Beyond virtual-passthrough, we introduce three additional DVH mechanisms: virtual timers, virtual inter-processor interrupts, and virtual idle. DVH provides virtual hardware for these mechanisms that mimics the underlying hardware and, in some cases, adds new enhancements that leverage the flexibility of software without the need for matching physical hardware support. We have implemented DVH in KVM. Our experimental results show that combining the four DVH mechanisms can provide even greater performance than virtual-passthrough alone and provide near-native execution speeds on real application workloads.

A thesis submitted to the Faculty of Engineering and the Built Environment in fulfilment of the requirements for the degree of Doctor of Philosophy, 2016 / Online resource (xii, 151 leaves) / Several meetings of the Extremely Large Databases Community for large scale scientific applications have advocated the use of multidimensional arrays as the appropriate model for representing scientific databases. Scientific databases gradually grow to massive sizes of the order of terabytes and petabytes. As such, the storage of such databases requires efficient dynamic storage schemes where the array is allowed to arbitrarily extend the bounds of the dimensions. Conventional multidimensional array representations in today’s programming environments do not extend or shrink their bounds without relocating elements of the data-set. In general extendibility of the bounds of the dimensions is limited to only one dimension. This thesis presents a technique for storing dense multidimensional arrays by chunks such that the array can be extended along any dimension without compromising the access time of an element. This is done with a computed access mapping function that maps the k-dimensional index onto a linear index of the storage locations. This concept forms the basis for the implementation of an array file of any number of dimensions, where the bounds of the array dimension can be extended arbitrarily. Such a feature currently exists in the Hierarchical Data Format version 5 (HDF5). However, extending the bound of a dimension in the HDF5 array file can be unusually expensive in time. Such extensions, in our storage scheme for dense array files, can be performed while still accessing elements of the array at orders of magnitude faster than in HDF5 or conventional array-files. We also present Parallel Chunked Extendible Dense Array (PEXTA), a new parallel I/O model for the Global Array Toolkit. PEXTA provides the necessary Application Programming Interface (API) for explicit data transfer between the memory resident global array and its secondary storage counterpart but also allows the persistent array to be extended on any dimension without compromising the access time of an element or sub-array elements. Such APIs provide a platform for high speed and parallel hyperspectral image processing without performance degradation, even when the imagery files undergo extensions. / MT2017

This research methodology isolates coding properties and identifies the probability of security vulnerabilities using machine learning and historical data. Several approaches characterize the effectiveness of detecting security-related bugs that manifest as vulnerabilities, but none utilize vulnerability patch information. The main contribution of this research is a framework to analyze LLVM Intermediate Representation Code and merging core source code representations using source code properties. This research is beneficial because it allows source programs to be transformed into a graphical form and users can extract specific code properties related to vulnerable functions. The result is an improved approach to detect, identify, and track software system vulnerabilities based on a performance evaluation. The methodology uses historical function level vulnerability information, unique feature extraction techniques, a novel code property graph, and learning algorithms to minimize the amount of end user domain knowledge necessary to detect vulnerabilities in applications. The analysis shows approximately 99% precision and recall to detect known vulnerabilities in the National Institute of Standards and Technology (NIST) Software Assurance Metrics and Tool Evaluation (SAMATE) project. Furthermore, 72% percent of the historical vulnerabilities in the OpenSSL testing environment were detected using a linear support vector classifier (SVC) model.

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The Advising Module: Graduate Application System is a Web-based application system that provides quality advice on coursework for prospective as well as continuing graduate students. It also serves as an improved tracking system for the graduate coordinator. Authorized parties may obtain access to status evaluations, master's options, and permitted course waivers, course listings, personal data, various advisement forms, application usage statistics, and automatic data updating process reports.

The main purpose of this project is to develop new functionalities for the Solicitation Management System (SMS) to support the Office of Technology Transfer and Commercialization (OTTC), California State University San Bernardino (CSUSB) and the Center for the Commercialization of Advanced Technology (CCAT), San Diego State University (SDSU) for the 2008 solicitation, which opened on 28 Jan 2008. SMS is a system built to facilitate the processing of grant proposal solicitations. The SMS was first built in 2004 and was primarily used by the OTTC, CSUSB for its solicitation activities. The new version of the SMS is more user friendly, so that it is easier for users to use and comprehend. The purpose of this software is to aid the processing of a solicitation for organizations that conduct solicitations for grant proposals.

Thesis (M. Tech.) - Central University of Technology, Free State, 2006 / A multi-threaded, multi-agent image recognition software application called RecMaster has been developed specifically for the purpose of quality control in a production environment. This entails using the system as a monitor to identify invalid objects moving on a conveyor belt and to pass on the relevant information to an attached device, such as a robotic arm, which will remove the invalid object. The main purpose of developing this system was to prove that a desktop computer could run an image recognition system efficiently, without the need for high-end, high-cost, specialised computer hardware. The programme operates by assigning each agent a task in the recognition process and then waiting for resources to become available. Tasks related to edge detection, colour inversion, image binarisation and perimeter determination were assigned to individual agents. Each agent is loaded onto its own processing thread, with some of the agents delegating their subtasks to other processing threads. This enables the application to utilise the available system resources more efficiently. The application is very limited in its scope, as it requires a uniform image background as well as little to no variance in camera zoom levels and object to lens distance. This study focused solely on the development of the application software, and not on the setting up of the actual imaging hardware. The imaging device, on which the system was tested, was a web cam capable of a 640 x 480 resolution. As such, all image capture and processing was done on images with a horizontal resolution of 640 pixels and a vertical resolution of 480 pixels, so as not to distort image quality. The application locates objects on an image feed - which can be in the format of a still image, a video file or a camera feed - and compares these objects to a model of the object that was created previously. The coordinates of the object are calculated and translated into coordinates on the conveyor system. These coordinates are then passed on to an external recipient, such as a robotic arm, via a serial link. The system has been applied to the model of a DVD, and tested against a variety of similar and dissimilar objects to determine its accuracy. The tests were run on both an AMD- and Intel-based desktop computer system, with the results indicating that both systems are capable of efficiently running the application. On average, the AMD-based system tended to be 81% faster at matching objects in still images, and 100% faster at matching objects in moving images. The system made matches within an average time frame of 250 ms, making the process fast enough to be used on an actual conveyor system. On still images, the results showed an 87% success rate for the AMD-based system, and 73% for Intel. For moving images, however, both systems showed a 100% success rate.

The development of enterprise software is a complex activity that requires a diverse set of stakeholders to communicate and coordinate in order to achieve a successful outcome. In this dissertation I introduce a high-level physical architecture for a platform titled FeatureIT that has the goal of supporting the collaboration between stakeholders throughout the entire Software Development Life Cycle (SDLC). FeatureIT is the result of unifying the theoretical foundations of the multi-disciplinary field of Computer Supported Cooperative Work (CSCW) with the paradigm and associated technologies of Web 2.0. The architecture was borne out a study of literature in the fields of CSCW, Web 2.0 and software engineering, which facilitated the identification of functional and non-functional requirements necessary for the platform. The design science research methodology was employed to construct this architecture iteratively to satisfy the requirements while validating its efficacy against a comprehensive set of scenarios that typically occur in the SDLC. / Computing / M. Sc. (Information Systems)

A dissertation submitted in full fulfillment of the requirements for the degree of the Master of Commerce, School of Economic and Business Sciences, University of the Witwatersrand, December 2016 / The increasing level of consumer engagement with smartphones and tablets or ipods, and the proliferation of mobile applications in recent years have seen a rapid growth in branded apps. Marketers are creating branded mobile apps as a brand communication channel to attract new customers and potentially increase brand loyalty among current customers. Previous research has measured initial adoption or intention to adopt branded apps rather than continuance adoption. In South Africa, few studies have explored adoption of branded apps among generation Y consumers. To fill this gap, this research aims to determine the effectiveness of branded mobile apps in driving brand loyalty among generation Y consumers. To achieve this goal, the research uses Expectation Confirmation Theory (ECT) to explore the factors influencing satisfaction, continuance adoption of branded apps and brand loyalty. Using a quantitative research approach, a total of 406 valid self-administered questionnaires were collected by survey method, and structural equation modelling was employed in the data analysis. The results indicate that confirmation of expectations–functional value, social value and satisfaction significantly influence brand loyalty. When consumers confirmed expectations of branded apps, it directly led to positive perceptions of value and satisfaction. Consumer satisfaction was a significant driver of behavioural loyalty. Results also suggested that consumer confirmation of expectations and perceptions of value impacted on continuance intention indirectly through satisfaction. Perceived functional value was found to be an important direct booster of consumer’s decisions and behaviour to continue using branded apps, while social value was found to be an inhibitor of continuance intention. The relationship between continuance intention and brand loyalty was insignificant. Continuance intention was simply an intermediate response following satisfaction with prior usage. This study therefore confirmed and extended the (ECT), that satisfaction with a product or service was a prerequisite for establishing continuance intention and brand loyalty among consumers. / XL2018