Fault tolerance via diversity for off-the-shelf products: A study with SQL database servers

If an off-the-shelf software product exhibits poor dependability due to design faults, then software fault tolerance is often the only way available to users and system integrators to alleviate the problem. Thanks to low acquisition costs, even using multiple versions of software in a parallel architecture, which is a scheme formerly reserved for few and highly critical applications, may become viable for many applications. We have studied the potential dependability gains from these solutions for off-the-shelf database servers. We based the study on the bug reports available for four off-the-shelf SQL servers plus later releases of two of them. We found that many of these faults cause systematic noncrash failures, which is a category ignored by most studies and standard implementations of fault tolerance for databases. Our observations suggest that diverse redundancy would be effective for tolerating design faults in this category of products. Only in very few cases would demands that triggered a bug in one server cause failures in another one, and there were no coincident failures in more than two of the servers. Use of different releases of the same product would also tolerate a significant fraction of the faults. We report our results and discuss their implications, the architectural options available for exploiting them, and the difficulties that they may present

HiTrust: building cross-organizational trust relationship based on a hybrid negotiation tree

Small-world phenomena have been observed in existing peer-to-peer (P2P) networks which has proved useful in the design of P2P file-sharing systems. Most studies of constructing small world behaviours on P2P are based on the concept of clustering peer nodes into groups, communities, or clusters. However, managing additional multilayer topology increases maintenance overhead, especially in highly dynamic environments. In this paper, we present Social-like P2P systems (Social-P2Ps) for object discovery by self-managing P2P topology with human tactics in social networks. In Social-P2Ps, queries are routed intelligently even with limited cached knowledge and node connections. Unlike community-based P2P file-sharing systems, we do not intend to create and maintain peer groups or communities consciously. In contrast, each node connects to other peer nodes with the same interests spontaneously by the result of daily searches

A demonstration of a service oriented virtual environment for complex system analysis

Distributed virtual simulation is increasingly in demand within the automotive industry. A distributed and networked approach to system level design and simulation stands to benefit from a unifying relational oriented modeling and simulation framework. This will permit innovative use of existing independent simulations for increased concurrency in design and verification and validation. This paper demonstrates an analysis of the vehicle as a complex system through the combination of a relational framework, high level syntax and semantics for representing models and distributed simulation. This promises to provide a rigorous, traceable and agile approach to conceptual vehicle design and analysis

Models of Reliability of Fault-Tolerant Software Under Cyber-Attacks

This paper offers a new approach to modelling the effect of cyber-attacks on reliability of software used in industrial control applications. The model is based on the view that successful cyber-attacks introduce failure regions, which are not present in non-compromised software. The model is then extended to cover a fault tolerant architecture, such as the 1-out-of-2 software, popular for building industrial protection systems. The model is used to study the effectiveness of software maintenance policies such as patching and "cleansing" ("proactive recovery") under different adversary models ranging from independent attacks to sophisticated synchronized attacks on the channels. We demonstrate that the effect of attacks on reliability of diverse software significantly depends on the adversary model. Under synchronized attacks system reliability may be more than an order of magnitude worse than under independent attacks on the channels. These findings, although not surprising, highlight the importance of using an adequate adversary model in the assessment of how effective various cyber-security controls are

Player protocols for football boot testing

Football is the most popular sport and played by more players worldwide than any other sport. The football boot industry is therefore big, competitive and still growing. Today, football boot designs are subcategorised into four categories, of which three are linked to specific skill performance enhancing claims: The power boot for enhanced shooting performance, the touch/control boot for enhanced ball control and the speed boot for enhanced speed generation. In comparison to the strong marketing claims, little research has been published on the impact of football boot design on performance, injury and comfort. Therefore, little is known about the importance and impact of changing boot design. The outcome of this thesis offers researcher and the football boot industry validated human test protocols for power boot, touch/control and speed boot designs. The outcome of the thesis also advances the knowledge of how the football boot impacts performance, comfort and highlights the potential links between plantar comfort and injury risk. Rule based system assessment was performed to validate a boot performance conceptual framework linking the player and their desired movements during a football match with the football boot and its different components. The three protocols for assessment of key performance aspects for power boots, touch/control boots and speed boots were validated using test-retest reliability assessment through relative and absolute reliability measures. The power boot protocols involved shooting assessment measuring ball velocity, offset from target, success and player perception of ball velocity and accuracy. The touch/control boot protocol involved dribbling and passing assessment measuring time, number of touches and radial distance from cones during completion of a complex dribbling drill, ball velocity and offset from target during flat and airborne passes. The speed boot protocols involved combined agility and acceleration sprinting time and jump height before and after a 90 min match simulation protocol. Throughout the match simulation heart rate, player perceived exertion, perceived muscle fatigue, overall foot comfort and specific regional foot comfort. The validated protocols were then applied to assess how boot parameters impact performance. For the power boot, boots with and without upper padding were compared II demonstrating a small favour for the non-padded boot. Similarly, boots with and without upper padding were compared for the touch/control boot scenario with no differences seen between the two designs. Finally, two commercially available speed boots were assessed for the speed boot scenario demonstrating significant differences in both comfort and performance measures. Indicating a potential link between decreased foot comfort and decreased ability to maintain performance throughout a 90 min game. The boot performance conceptual framework was developed with component at each level but no interactive links between levels were added due to the lack of evidence in the literature. The boot performance conceptual framework offers researchers and the football boot industry a visualisation tool to aid the general overview when assessing or designing football boots. The three validations of protocols demonstrated strong test- retest reliability for most measures assessed and can therefore be applied to assess the impact of altering boot designs like demonstrated in this study

Should sex ratio distorting parasites abandon horizontal transmission?

BACKGROUND: Sex-ratio distorting parasites are of interest due to their effects upon host population dynamics and their potential to influence the evolution of host sex determination systems. In theory, the ability to distort host sex-ratios allows a parasite with efficient vertical (hereditary) transmission to dispense completely with horizontal (infectious) transmission. However, recent empirical studies indicate that some sex-ratio distorting parasites have retained the capability for horizontal transmission. RESULTS: Numerical simulations using biologically realistic parameters suggest that a feminising parasite is only likely to lose the capability for horizontal transmission if its host occurs at low density and/or has a male-biased primary sex ratio. It is also demonstrated that even a small amount of horizontal transmission can allow multiple feminising parasites to coexist within a single host population. Finally it is shown that, by boosting its host's rate of population growth, a feminising parasite can increase its own horizontal transmission and allow the invasion of other, more virulent parasites. CONCLUSIONS: The prediction that sex-ratio distorting parasites are likely to retain a degree of horizontal transmission has important implications for the epidemiology and host-parasite interactions of these organisms. It may also explain the frequent co-occurrence of several sex-ratio distorting parasite species in nature

GA-Par: Dependable Microservice Orchestration Framework for Geo-Distributed Clouds

Recent advances in composing Cloud applications have been driven by deployments of inter-networking heterogeneous microservices across multiple Cloud datacenters. System dependability has been of the upmost importance and criticality to both service vendors and customers. Security, a measurable attribute, is increasingly regarded as the representative example of dependability. Literally, with the increment of microservice types and dynamicity, applications are exposed to aggravated internal security threats and externally environmental uncertainties. Existing work mainly focuses on the QoS-aware composition of native VM-based Cloud application components, while ignoring uncertainties and security risks among interactive and interdependent container-based microservices. Still, orchestrating a set of microservices across datacenters under those constraints remains computationally intractable. This paper describes a new dependable microservice orchestration framework GA-Par to effectively select and deploy microservices whilst reducing the discrepancy between user security requirements and actual service provision. We adopt a hybrid (both whitebox and blackbox based) approach to measure the satisfaction of security requirement and the environmental impact of network QoS on system dependability. Due to the exponential grow of solution space, we develop a parallel Genetic Algorithm framework based on Spark to accelerate the operations for calculating the optimal or near-optimal solution. Large-scale real world datasets are utilized to validate models and orchestration approach. Experiments show that our solution outperforms the greedy-based security aware method with 42.34 percent improvement. GA-Par is roughly 4× faster than a Hadoop-based genetic algorithm solver and the effectiveness can be constantly guaranteed under different application scales

Uncertainty explicit assessment of off-the-shelf software: A Bayesian approach

Assessment of software COTS components is an essential part of component-based software development. Poorly chosen components may lead to solutions of low quality and that are difficult to maintain. The assessment may be based on incomplete knowledge about the COTS component itself and other aspects (e.g. vendor’s credentials, etc.), which may affect the decision of selecting COTS component(s). We argue in favor of assessment methods in which uncertainty is explicitly represented (‘uncertainty explicit’ methods) using probability distributions. We provide details of a Bayesian model, which can be used to capture the uncertainties in the simultaneous assessment of two attributes, thus, also capturing the dependencies that might exist between them. We also provide empirical data from the use of this method for the assessment of off-the-shelf database servers which illustrate the advantages of ‘uncertainty explicit’ methods over conventional methods of COTS component assessment which assume that at the end of the assessment the values of the attributes become known with certainty

An initial evaluation of an online, compassionate intervention for adults with type 1 and type 2 Diabetes Mellitus

Background: Individuals with a Chronic Physical Health Condition (CPHC) may experience ongoing challenges with physical and psychological wellbeing. Psychological therapies are offered to this population and literature is emerging to indicate that compassion-focused interventions may be useful. This review sought to assess the evidence-base for the effectiveness and acceptability of digital, self-compassion interventions for individuals with CPHCs. Methods: A quantitative, systematic review of five databases (four published, one unpublished) elicited 12 studies that met inclusion criteria. Studies were assessed for quality using the Effective Public Healthcare Practice Project tool. Data was extracted and narratively synthesised. Results: Included studies were of a weak (n=7) or moderate quality (n=5), with samples of chronic pain, visible skin conditions, breast cancer survivors, type two diabetes mellitus, coeliac disease and mixed CPHC populations. Findings suggested preliminary evidence for the effectiveness and acceptability of digital, self-compassion interventions in CPHCs, particularly in people with chronic pain and breast cancer survivors. This was reflected in the change of self-compassion, psychological and condition-specific outcome measures, along with reported satisfaction and adherence Discussion: Given the preliminary findings, digital, self-compassion interventions appear to be effective and acceptable for some CPHCs. Suggestions for future research have been made in the context of the reported strengths and limitations of this systematic review