Access Schema Research Articles

Bounded Graph Pattern Matching With View

Bounded evaluation using views is to compute the answers $Q({\cal D})$ to a query $Q$ in a dataset ${\cal D}$ by accessing only cached views and a small fraction $D_Q$ of ${\cal D}$ such that the size $|D_Q|$ of $D_Q$ and the time to identify $D_Q$ are independent of $|{\cal D}|$, no matter how big ${\cal D}$ is. Though proven effective for relational data, it has yet been investigated for graph data. In light of this, we study the problem of bounded pattern matching using views. We first introduce access schema ${\cal C}$ for graphs and propose a notion of joint containment to characterize bounded pattern matching using views. We show that a pattern query $\sq$ can be boundedly evaluated using views ${\cal V}(G)$ and a fraction $G_Q$ of $G$ if and only if the query $\sq$ is jointly contained by ${\cal V}$ and ${\cal C}$. Based on the characterization, we develop an efficient algorithm as well as an optimization strategy to compute matches by using ${\cal V}(G)$ and $G_Q$. Using real-life and synthetic data, we experimentally verify the performance of these algorithms, and show that (a) our algorithm for joint containment determination is not only effective but also efficient; and (b) our matching algorithm significantly outperforms its counterpart, and the optimization technique can further improve performance by eliminating unnecessary input.

Bounded Evaluation: Querying Big Data with Bounded Resources

This work aims to reduce queries on big data to computations on small data, and hence make querying big data possible under bounded resources. A query Q is boundedly evaluable when posed on any big dataset {cal D}, there exists a fraction {{cal D}_Q} of {cal D} such that Q({cal D}) = Q({{cal D}_Q}), and the cost of identifying {{cal D}_Q} is independent of the size of {cal D}. It has been shown that with an auxiliary structure known as access schema, many queries in relational algebra (RA) are boundedly evaluable under the set semantics of RA. This paper extends the theory of bounded evaluation to RAaggr, i.e., RA extended with aggregation, under the bag semantics. (1) We extend access schema to bag access schema, to help us identify {{cal D}_Q} for RAaggr queries Q. (2) While it is undecidable to determine whether an RAaggr query is boundedly evaluable under a bag access schema, we identify special cases that are decidable and practical. (3) In addition, we develop an effective syntax for bounded RAaggr queries, i.e., a core subclass of boundedly evaluable RAaggr queries without sacrificing their expressive power. (4) Based on the effective syntax, we provide efficient algorithms to check the bounded evaluability of RAaggr queries and to generate query plans for bounded RAaggr queries. (5) As proof of concept, we extend PostgreSQL to support bounded evaluation. We experimentally verify that the extended system improves performance by orders of magnitude.

Data driven approximation with bounded resources

This paper proposes BEAS, a resource-bounded scheme for querying relations. It is parameterized with a resource ratio α ∈ (0,1], indicating that given a big dataset D , we can only afford to access an α -fraction of D with limited resources. For a query Q posed on D , BEAS computes exact answers Q(D) if doable and otherwise approximate answers, by accessing at most α | D | amount of data in the entire process. Underlying BEAS are (1) an access schema, which helps us identify and fetch the part of data needed to answer Q , (2) an accuracy measure to assess approximate answers in terms of their relevance and coverage w.r.t . exact answers, (3) an Approximability Theorem for the feasibility of resource-bounded approximation, and (4) algorithms for query evaluation with bounded resources. A unique feature of BEAS is its ability to answer unpredictable queries, aggregate or not, using bounded resources and assuring a deterministic accuracy lower bound. Using real-life and synthetic data, we empirically verify the effectiveness and efficiency of BEAS.

Enabling LTE and WiFi Coexisting in 5 GHz for Efficient Spectrum Utilization

Due to the increasing mobile traffic demands in cellular network, researchers have proposed the coexistence of LTE and WiFi technologies in 5 GHz unlicensed bands. Therefore, how to efficiently utilize the spectrum in 5 GHz becomes extremely important. To avoid the channel access conflicts, current LTE Unlicensed (LTE-U) technology introduces the duty cycle of LTE, while License-Assisted Access (LAA) technology introduces Listen-Before-Talk (LBT) mechanism. While these two technologies improve the spectrum utilization by using time division access schema, we believe that more efficient spectrum utilization can be achieved by enabling simultaneous transmissions from LTE and WiFi. In this paper, we propose a novel method (i.e.,Low Amplitude Stream Injection (LASI) method) to enable the simultaneous transmissions of WiFi and LTE frames in the same channel and recover the data from the conflicts. To further utilize theLASImethod, we introduce theConflict-Tolerant Channel Allocation (CTCA)algorithm to optimize the channel allocation and achieve more efficient spectrum utilization in 5 GHz. Extensive simulation results show that our approach achieves lower latency and higher throughput. Compared with the state-of-the-art LTE-U and LAA technologies, our approach can improve the spectrum efficiency 2.9 times.

Assessing the Primary Data Hosted by the Spanish Node of the Global Biodiversity Information Facility (GBIF)

In order to effectively understand and cope with the current ‘biodiversity crisis’, having large-enough sets of qualified data is necessary. Information facilitators such as the Global Biodiversity Information Facility (GBIF) are ensuring increasing availability of primary biodiversity records by linking data collections spread over several institutions that have agreed to publish their data in a common access schema. We have assessed the primary records that one such publisher, the Spanish node of GBIF (GBIF.ES), hosts on behalf of a number of institutions, considered to be a highly representative sample of the total mass of available data for a country in order to know the quantity and quality of the information made available. Our results may provide an indication of the overall fitness-for-use in these data. We have found a number of patterns in the availability and accrual of data that seem to arise naturally from the digitization processes. Knowing these patterns and features may help deciding when and how these data can be used. Broadly, the error level seems low. The available data may be of capital importance for the development of biodiversity research, both locally and globally. However, wide swaths of records lack data elements such as georeferencing or taxonomical levels. Although the remaining information is ample and fit for many uses, improving the completeness of the records would likely increase the usability span for these data.

Progressive Data Synchronization Model for Mobile Devices

Mobile data synchronization is an important technique used to replicate or synchronize data between a mobile client and a remote server. It helps overcome unstable wireless networks and support the disconnected operation. The current state of mobile data synchronization is most successful at transparently synchronizing all data. Generally, once a synchronization feature enabled, data is automatically synchronized without offering a fine grained and customizable synchronization policy. Furthermore, the context information, such as localization, date, device overload and resource consumption, type and quality of the connection, etc., are not equally taken into account or not considered at all. One solution is to develop a synchronization model that rely on a fine grained and flexible synchronization policy and where context information is considered as first-class citizen. This article puts forward a new model of data synchronization in mobile devices based on progressive data access schema.

Arquitectura Basada en Inteligencia Artificial Distribuida para la Gerencia Integrada de Producción Industrial

This proposal consists in reference architecture for the integrated production management, which allows the access to the required information about the state of the productive process and the development of the business processes´ intelligent automation. This architecture is composed by a standardized production information access schema, an ontological framework and a business processes automation mechanism, based on distributed artificial intelligence techniques, specifically multi-agent systems and electronic institutions.

Biological Information Standards

Biological Information Standards