72,844 research outputs found
Middleware-based Database Replication: The Gaps between Theory and Practice
The need for high availability and performance in data management systems has
been fueling a long running interest in database replication from both academia
and industry. However, academic groups often attack replication problems in
isolation, overlooking the need for completeness in their solutions, while
commercial teams take a holistic approach that often misses opportunities for
fundamental innovation. This has created over time a gap between academic
research and industrial practice.
This paper aims to characterize the gap along three axes: performance,
availability, and administration. We build on our own experience developing and
deploying replication systems in commercial and academic settings, as well as
on a large body of prior related work. We sift through representative examples
from the last decade of open-source, academic, and commercial database
replication systems and combine this material with case studies from real
systems deployed at Fortune 500 customers. We propose two agendas, one for
academic research and one for industrial R&D, which we believe can bridge the
gap within 5-10 years. This way, we hope to both motivate and help researchers
in making the theory and practice of middleware-based database replication more
relevant to each other.Comment: 14 pages. Appears in Proc. ACM SIGMOD International Conference on
Management of Data, Vancouver, Canada, June 200
Architecture for Mobile Heterogeneous Multi Domain Networks
Multi domain networks can be used in several scenarios including military, enterprize networks, emergency networks and many other cases. In such networks, each domain might be under its own administration. Therefore, the cooperation among domains is conditioned by individual domain policies regarding sharing information, such as network topology, connectivity, mobility, security, various service availability and so on. We propose a new architecture for Heterogeneous Multi Domain (HMD) networks, in which one the operations are subject to specific domain policies. We propose a hierarchical architecture, with an infrastructure of gateways at highest-control level that enables policy based interconnection, mobility and other services among domains. Gateways are responsible for translation among different communication protocols, including routing, signalling, and security. Besides the architecture, we discuss in more details the mobility and adaptive capacity of services in HMD. We discuss the HMD scalability and other advantages compared to existing architectural and mobility solutions. Furthermore, we analyze the dynamic availability at the control level of the hierarchy
Storage Solutions for Big Data Systems: A Qualitative Study and Comparison
Big data systems development is full of challenges in view of the variety of
application areas and domains that this technology promises to serve.
Typically, fundamental design decisions involved in big data systems design
include choosing appropriate storage and computing infrastructures. In this age
of heterogeneous systems that integrate different technologies for optimized
solution to a specific real world problem, big data system are not an exception
to any such rule. As far as the storage aspect of any big data system is
concerned, the primary facet in this regard is a storage infrastructure and
NoSQL seems to be the right technology that fulfills its requirements. However,
every big data application has variable data characteristics and thus, the
corresponding data fits into a different data model. This paper presents
feature and use case analysis and comparison of the four main data models
namely document oriented, key value, graph and wide column. Moreover, a feature
analysis of 80 NoSQL solutions has been provided, elaborating on the criteria
and points that a developer must consider while making a possible choice.
Typically, big data storage needs to communicate with the execution engine and
other processing and visualization technologies to create a comprehensive
solution. This brings forth second facet of big data storage, big data file
formats, into picture. The second half of the research paper compares the
advantages, shortcomings and possible use cases of available big data file
formats for Hadoop, which is the foundation for most big data computing
technologies. Decentralized storage and blockchain are seen as the next
generation of big data storage and its challenges and future prospects have
also been discussed
H2O: An Autonomic, Resource-Aware Distributed Database System
This paper presents the design of an autonomic, resource-aware distributed
database which enables data to be backed up and shared without complex manual
administration. The database, H2O, is designed to make use of unused resources
on workstation machines. Creating and maintaining highly-available, replicated
database systems can be difficult for untrained users, and costly for IT
departments. H2O reduces the need for manual administration by autonomically
replicating data and load-balancing across machines in an enterprise.
Provisioning hardware to run a database system can be unnecessarily costly as
most organizations already possess large quantities of idle resources in
workstation machines. H2O is designed to utilize this unused capacity by using
resource availability information to place data and plan queries over
workstation machines that are already being used for other tasks. This paper
discusses the requirements for such a system and presents the design and
implementation of H2O.Comment: Presented at SICSA PhD Conference 2010 (http://www.sicsaconf.org/
A Taxonomy of Data Grids for Distributed Data Sharing, Management and Processing
Data Grids have been adopted as the platform for scientific communities that
need to share, access, transport, process and manage large data collections
distributed worldwide. They combine high-end computing technologies with
high-performance networking and wide-area storage management techniques. In
this paper, we discuss the key concepts behind Data Grids and compare them with
other data sharing and distribution paradigms such as content delivery
networks, peer-to-peer networks and distributed databases. We then provide
comprehensive taxonomies that cover various aspects of architecture, data
transportation, data replication and resource allocation and scheduling.
Finally, we map the proposed taxonomy to various Data Grid systems not only to
validate the taxonomy but also to identify areas for future exploration.
Through this taxonomy, we aim to categorise existing systems to better
understand their goals and their methodology. This would help evaluate their
applicability for solving similar problems. This taxonomy also provides a "gap
analysis" of this area through which researchers can potentially identify new
issues for investigation. Finally, we hope that the proposed taxonomy and
mapping also helps to provide an easy way for new practitioners to understand
this complex area of research.Comment: 46 pages, 16 figures, Technical Repor
Two meta-analyses of noncontact healing studies
Reviews of empirical work on the efficacy of noncontact healing have found that interceding on behalf of patients through prayer or by adopting various practices that incorporate an intention to heal can have some positive effect upon their wellbeing. However, reviewers have also raised concerns about study quality and the diversity of healing approaches adopted, which makes the findings difficult to interpret. Some of these concerns can be addressed by adopting a standardised approach based on the double-blind randomised controlled clinical trial, and a recent review restricted to such studies has reported a combined effect size of .40 (p < .001). However, the studies in this review involve human participants for whom there can be no guarantee that control patients are not beneficiaries of healing intentions from friends, family or their own religious groups. We proposed to address this by reviewing healing studies that involved biological systems other than ‘whole’ humans (i.e. to include animal and plant work but also work involving human biological matter such as blood samples or cell cultures), which are less susceptible to placebo and expectancy effects and also allow for more circumscribed outcome measures. Secondly, doubts have been cast concerning the legitimacy of some of the work included in previous reviews so we planned to conduct an updated review that excluded that work. For phase 1, 49 non-whole human studies from 34 papers were eligible for review. The combined effect size weighted by sample size yielded a highly significant r of .258. However the effect sizes in the database were heterogeneous, and outcomes correlated with blind ratings of study quality. When restricted to studies that met minimum quality thresholds, the remaining 22 studies gave a reduced but still significant weighted r of .115. For phase 2, 57 whole human studies across 56 papers were eligible for review. When combined, these studies yielded a small effect size of r = .203 that was also significant. This database was also heterogeneous, and outcomes were correlated with methodological quality ratings. However, when restricted to studies that met threshold quality levels the weighted effect size for the 27 surviving studies increased to r = .224. Taken together these results suggest that subjects in the active condition exhibit a significant improvement in wellbeing relative to control subjects under circumstances that do not seem to be susceptible to placebo and expectancy effects. Findings with the whole human database gave a smaller mean effect size but this was still significant and suggests that the effect is not dependent upon the previous inclusion of suspect studies and is robust enough to accommodate some high profile failures to replicate. Both databases show problems with heterogeneity and with study quality and recommendations are made for necessary standards for future replication attempts
A coupled drug kinetics-cell cycle model to analyse the response of human cells to intervention by topotecan
A model describing the response of the growth of single human cells in the absence and presence of the anti-cancer agent topotecan (TPT) is presented. The model includes a novel coupling of both the kinetics of TPT and cell cycle responses to the agent. By linking the models in this way, rather than using separate (disjoint) approaches, it is possible to illustrate how the drug perturbs the cell cycle. The model is compared to experimental in vitro cell cycle response data (comprising single cell descriptors for molecular and behavioural events), showing good qualitative agreement for a range of TPT dose levels
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