Promising directions for the development of modern databases

In this article, we will compare the SQL and NoSQL models, their advantages and disadvantages, clarify the variations of using both approaches to database management and explain in which cases it is better to use one or the other model. Three main characteristics of the system were tested: parallel data processing, working with information stores, and data replication. The possibility of parallel data processing was evaluated by analyzing the mechanisms of blocking, multi-level parallel access control and ACID. Storage testing covered both physical media and RAM usage. Replication was tested in synchronous and asynchronous modes. During the tests, we found out that SQL databases with the possibility of clustering showed promising performance results per node and also have scalability.

Ensemble Statistics Accessed through Proxies: Range Heuristic and Dependence on Low-Level Properties in Variability Discrimination

People can quickly and accurately compute not only the mean size of a set of items but also the size variability of the items. However, it remains unknown how these statistics are estimated. Here we show that neither parallel access to all items nor random subsampling of just a few items is sufficient to explain participants' estimations of size variability. In three experiments, we had participants compare two arrays of circles with different variability in their sizes. In the first 2 experiments, we manipulated the congruency of the range and variance of the arrays. The arrays with congruent range and variability information were judged more accurately, indicating the use of range as a proxy for variability. Experiments 2B and 3 showed that people also are not invariant to low- or mid-level visual information in the arrays, as comparing arrays with different low-level characteristics (filled vs. outlined circles) led to systematic biases. Together, these experiments indicate that range and low- or mid-level properties are both utilized as proxies for variability discrimination, and people are flexible in adopting these strategies. These strategies are at odds with the claim of parallel extraction of ensemble statistics per se and random subsampling strategies previously proposed in the literature.

Parallel Access Control Model in Cross-Domain Grid Computing Environment

Despite the various attractive features that grid computing has to offer, it has many great security challenges, such as access control. With the expansion of the network scale, a large number of authorization requests have to be treated; on the other hand, the multi-domain nature of grid computing generates difficult to manage questions about cross-domain access control, and a variety of solutions use the role mapping mechanism to allow collaborations between domains. But this mechanism gives a potential risk of violating consistency properties of domains. This article aims to address this issue and proposes a parallel access control model in cross-domain grid computing architecture to be more convenient to the security requirements of the multi-domain environment. Finally, as a proof of concept, the authors implement a cross-domain and parallel authorization simulator (CD-PAS) where experiments are done. The obtained results show that the proposed model is sensitive to the number of authorization requests. In addition, it can effectively reduce the execution time of access control mechanism.

The Multiple-Orientability Thresholds for Random Hypergraphs

Ak-uniform hypergraphH= (V, E) is called ℓ-orientable if there is an assignment of each edgee∈Eto one of its verticesv∈esuch that no vertex is assigned more than ℓ edges. LetHn,m,kbe a hypergraph, drawn uniformly at random from the set of allk-uniform hypergraphs withnvertices andmedges. In this paper we establish the threshold for the ℓ-orientability ofHn,m,kfor allk⩾ 3 and ℓ ⩾ 2, that is, we determine a critical quantityc*k,ℓsuch that with probability 1 −o(1) the graphHn,cn,khas an ℓ-orientation ifc<c*k,ℓ, but fails to do so ifc>c*k,ℓ.Our result has various applications, including sharp load thresholds for cuckoo hashing, load balancing with guaranteed maximum load, and massive parallel access to hard disk arrays.