Index Query Research Articles

EURQ: A New Web Search‐based Uncertainty Index

Measuring economic uncertainty is extremely important for evaluating its role in economic activity. Nevertheless, measuring uncertainty is a difficult task since we do not know when economic agents perceive uncertainty and which type of uncertainty affects them. This paper introduces the economic uncertainty related queries (EURQ) index, computed for both the USA and Italy, which measures economic, political and normative uncertainty through large‐scale searches on the internet. We show that the EURQ index captures economic agents’ need for information in response to uncertainty shocks. Moreover, we show that this need for information is not just curiosity triggered by press coverage but rather captures individuals’ genuine interest, particularly in specific topics subject to uncertainty. Hence the EURQ index can be exploited fruitfully to measure the level of uncertainty perceived by economic agents and to assess the role of specific types of uncertainty in economic activity.

Location based Continuous Query Processing over Geo-streaming Data

In recent years, many data-intensive and location based applications have emerged that need to process stream data in applications such as network monitoring, telecommunications data management, and sensor networks. Unlike regular queries, a continuous query exists for certain period of time and need to be continuously processed during this time. The algorithms used for data processing for the traditional database systems are not suited to tackle complex and various continuous queries over dynamic streaming data. The indexing for finite queries is preferred to indexing on infinite data to avoid expensive operations of index maintenance. Previous related work focused on moving queries on static objects or static queries on moving object. But now-a-days queries as well as objects are dynamic. So, hybrid indexing for queries significantly reduces the space costs and scales well with the increasing data. To deal with the speed of unbounded data, it is necessary to use data parallelism in query processing. The data parallelism in query processing offers better performance, availability and scalability.

NEIST: A Neural-Enhanced Index for Spatio-Temporal Queries

Previous work on the spatio-temporal index often adopts a simple linear model to predict the future positions of moving objects, which may generate numerous errors for complex road networks and fast moving objects. In this paper, we propose NEIST, a neural-enhanced index to process spatio-temporal queries with enhanced efficiency and accuracy, by intelligently leveraging the movement patterns among moving objects. NEIST applies a Recurrent Neural Network (RNN) model to predict future positions of moving objects based on observed trajectories. To reduce the prediction overhead, a suffix-tree is further built to index trajectories with similar suffixes, and thus similar objects within a given similarity bound are grouped together to share the same prediction result. A prediction result in NEIST represents possible positions of a group of moving objects in the next t time slots. Inside each time slot, traditional linear prediction model is then adopted and a TPR-Tree is built to support spatio-temporal queries. We use Singapore and Porto taxi trajectory datasets to evaluate NEIST. Compared to previous approaches, NEIST achieves a much more efficient query performance and is able to produce about 70 percent more accurate results.

ELII: A novel inverted index for fast temporal query, with application to a large Covid-19 EHR dataset

Fast temporal query on large EHR-derived data sources presents an emerging big data challenge, as this query modality is intractable using conventional strategies that have not focused on addressing Covid-19-related research needs at scale. We introduce a novel approach called Event-level Inverted Index (ELII) to optimize time trade-offs between one-time batch preprocessing and subsequent open-ended, user-specified temporal queries. An experimental temporal query engine has been implemented in a NoSQL database using our new ELII strategy. Near-real-time performance was achieved on a large Covid-19 EHR dataset, with 1.3 million unique patients and 3.76 billion records. We evaluated the performance of ELII on several types of queries: classical (non-temporal), absolute temporal, and relative temporal. Our experimental results indicate that ELII accomplished these queries in seconds, achieving average speed accelerations of 26.8 times on relative temporal query, 88.6 times on absolute temporal query, and 1037.6 times on classical query compared to a baseline approach without using ELII. Our study suggests that ELII is a promising approach supporting fast temporal query, an important mode of cohort development for Covid-19 studies.

Query Indexing and Cluster-based Indexing Model for the Document Retrieval

Query Indexing and Cluster-based Indexing Model for the Document Retrieval

Privacy‐Guarding Optimal Route Finding with Support for Semantic Search on Encrypted Graph in Cloud Computing Scenario

The arrival of cloud computing age makes data outsourcing an important and convenient application. More and more individuals and organizations outsource large amounts of graph data to the cloud computing platform (CCP) for the sake of saving cost. As the server on CCP is not completely honest and trustworthy, the outsourcing graph data are usually encrypted before they are sent to CCP. The optimal route finding on graph data is a popular operation which is frequently used in many fields. The optimal route finding with support for semantic search has stronger query capabilities, and a consumer can use similar words of graph vertices as query terms to implement optimal route finding. Due to encrypting the outsourcing graph data before they are sent to CCP, it is not easy for data customers to manipulate and further use the encrypted graph data. In this paper, we present a solution to execute privacy‐guarding optimal route finding with support for semantic search on the encrypted graph in the cloud computing scenario (PORF). We designed a scheme by building secure query index to implement optimal route finding with support for semantic search based on searchable encryption idea and stemmer mechanism. We give formal security analysis for our scheme. We also analyze the efficiency of our scheme through the experimental evaluation.

Ext-LOUDS: A Space Efficient Extended LOUDS Index for Superset Query

Superset query is widely used in object-oriented databases, data mining, and many other fields. Trie is an efficient index for superset query, whereas most existing trie index aim at improving query performance while ignoring storage overheads. To solve this problem, in this paper, we propose an efficient extended Level-Ordered Unary Degree Sequence (LOUDS) index: Ext-LOUDS. Ext-LOUDS expresses a trie by 1 integer vector and 3 bit vectors directly map each NodeID to its corresponding position, thus accelerating some key operations needed for superset query. Based on Ext-LOUDS, an efficient superset query algorithm, ELOUDS-Super, is designed. Experimental results on both real and synthetic datasets show that Ext-LOUDS can decrease 50%–60% space overheads compared with trie while maintaining a relative good query performance.

The impact of political instability driven by the Tunisian revolution on the relationship between Google search queries index and financial market dynamics

PurposeThis paper examines the impact of political instability on the investors' behavior, measured by Google search queries, and on the dynamics of stock market returns.Design/methodology/approachFirst, by using the DCC-GARCH model, the authors examine the effect of investor sentiment on the Tunisian stock market return. Second, the authors employ the fully modified dynamic ordinary least square method (FMOL) to estimate the long-term relationship between investor sentiment and Tunisian stock market return. Finally, the authors use the wavelet coherence model to test the co-movement between investor sentiment measured by Google Trends and Tunisian stock market return.FindingsUsing the dynamic conditional correlation (DCC), the authors find that Google search queries index has the ability to reflect political events especially the Tunisian revolution. In addition, empirical results of fully modified ordinary least square (FMOLS) method reveal that Google search queries index has a slightly higher effect on Tunindex return after the Tunisian revolution than before this revolution. Furthermore, by employing wavelet coherence model, the authors find strong comovement between Google search queries index and return index during the period of the Tunisian revolution political instability. Moreover, in the frequency domain, strong coherence can be found in less than four months and in 16–32 months during the Tunisian revolution which show that the Google search queries measure was leading over Tunindex return. In fact, wavelet coherence analysis confirms the result of DCC that Google search queries index has the ability to detect the behavior of Tunisian investors especially during the period of political instability.Research limitations/implicationsThis study provides empirical evidence to portfolio managers that may use Google search queries index as a robust measure of investor's sentiment to select a suitable investment and to make an optimal investments decisions.Originality/valueThe important research question of how political instability affects stock market dynamics has been neglected by scholars. This paper attempts principally to fill this void by investigating the time-varying interactions between market returns, volatility and Google search based index, especially during Tunisian revolution.

Simpler FM-index for parameterized string matching

In parameterized string matching, a string comprises static and parameterized symbols. Two strings are said to be matched if there exists a one-to-one mapping of parameterized symbols onto itself such that it transforms one string into the other. Traditionally, to construct a full-text index for this problem, suffixes are transformed in a manner referred to as previous occurrence encoding. Although a space-efficient backward searching based data structure has been proposed recently, the data structure is specialized and complex owing to the nature of the encoding scheme. In this study, we demonstrate that a slight modification of the encoding scheme, by using ∞ instead of 0 to denote the first occurrences of each parameterized symbol, enables us to develop a much simpler FM-index for this problem, which only comprises two wavelet trees and one range maximum query index.

Forecasting Tourist Arrivals via Random Forest and Long Short-term Memory

In recent years, deep learning has been attracting substantial attention due to its outstanding forecasting performance. However, the application of deep learning methods in solving the problem of forecasting tourist arrivals has been few. For the efficient allocation of tourism resources, tourist arrivals must be accurately predicted for government and tourism enterprises. In this study, a new hybrid deep learning approach is developed for tourist arrival forecasting. Random forest is used to reduce the dimensionality of the search query index data for selecting a small subset of informative features that contain the information that is most related to the tourist arrivals. Differential evolution algorithm is designed for choosing the lag lengths of each search query index and historical tourist arrival data for reconstructing the forecasting input. Long short-term memory (LSTM) is used for modeling the nonlinear relationship between tourist arrivals and search query index data. Two comparative examples, namely, Beijing City and Jiuzhaigou Valley, are applied for verification of the forecasting accuracy of the proposed deep learning method. The results indicate that the proposed deep learning method outperforms some time series and machine learning methods.

Various aspects of retention index usage for GC-MS library search: A statistical investigation using a diverse data set

This work is devoted to the large-scale statistical evaluation of various aspects of using the retention index for GC-MS library search with a diverse data set. A search in a large library often does not give a correct compound even if a library contains it. One of the methods to improve a spectral library search procedure is to use the retention index information. The aim of this study is to explore some statistical peculiarities which can be helpful for development of automated software which uses a library search of diverse completely unknown compounds in a large database. A data set that was used in this work as a source of queries contains ~11 thousand spectra of compounds which belong to diverse chemical classes. Six equations for matching reference and experimental “retention index – spectrum” pairs were compared. It was found that good results can be obtained when a linear equation for similarity of pairs is used. Similarity of pairs is found as a sum of spectral similarity and of a product of a negative adjustable weight parameter and the absolute difference between reference and query retention indices. This equation performs equal or better than much more complex equations which contain two instead of one adjustable parameters. Widely used threshold-based approach, when candidates with high retention index deviation are rejected, performs worse than other equations. The use of predicted with neural networks retention indices as reference was also considered. Modern universal retention prediction models which are applicable to a wide variety of compounds are still quite inaccurate comparing with values from databases, but these predicted values allow to improve a library search as well. When predicted retention indices are used as reference, the linear equation for matching “retention index – spectrum” pairs also performs equal or better than other equations. The distribution of differences between query indices and reference indices (both calculated and experimental) was found close to exponential distribution near zero. The dependence of a fraction of correct identifications on the reference retention indices accuracy was studied. The addition of random noise with double exponential distribution to exact values was used to create “reference” retention indices with the predefined accuracy. The use of the molecular mass and molecular formula as additional constraints during a library search was also considered.

An Efficient Network Coding-based Air Index for Queries in Road Networks

An Efficient Network Coding-based Air Index for Queries in Road Networks

Predicting Bitcoin returns: Comparing the roles of newspaper- and internet search-based measures of uncertainty

We compare the ability of a newspaper-based measure and an internet search-based measure of uncertainty in predicting Bitcoin returns. Based on monthly data, we show that Bitcoin is a hedge against both measures. However, the predictive ability of the internet-based economic uncertainty related queries index is statistically stronger than the measure of uncertainty derived from newspapers in predicting Bitcoin returns, which is possibly due to the fact that the former measure of uncertainty is directly obtained by the individual investors, based on their search of the internet for terms related to uncertainty. This result is confirmed by various additional analyses.

The Most Likely Object to be Seen Through a Window

We study data structures to answer window queries using stochastic input sequences. The first problem is the most likely maximal point in a query window: Let [Formula: see text] be constants, with [Formula: see text]. Let [Formula: see text] be a set of [Formula: see text] points in [Formula: see text], for some fixed [Formula: see text]. For [Formula: see text], each point in [Formula: see text] is associated with a probability [Formula: see text] of existence. A point [Formula: see text] in [Formula: see text] is on the maximal layer of [Formula: see text] if there is no other point [Formula: see text] in [Formula: see text] such that [Formula: see text]. Consider a random subset of [Formula: see text] obtained by including, for [Formula: see text], each point of [Formula: see text] independently with probability [Formula: see text]. For a query interval [Formula: see text], with [Formula: see text], we report the point in [Formula: see text] that has the highest probability to be on the maximal layer of [Formula: see text] in [Formula: see text] time using [Formula: see text] space. We solve a special problem as follows. A sequence [Formula: see text] of [Formula: see text] points in [Formula: see text] is given ([Formula: see text]), where each point [Formula: see text] has a probability [Formula: see text] of existence associated with it. Given a query interval [Formula: see text] and an integer [Formula: see text] with [Formula: see text], we report the probability of [Formula: see text] to be on the maximal layer of [Formula: see text] in [Formula: see text] time using [Formula: see text] space. The second problem we consider is the most likely common element problem. Let [Formula: see text] be the universe. Let [Formula: see text] be a sequence of random subsets of [Formula: see text] such that for [Formula: see text] and [Formula: see text], element [Formula: see text] is added to [Formula: see text] with probability [Formula: see text] (independently of other choices). Let [Formula: see text] be a fixed real number with [Formula: see text]. For query indices [Formula: see text], [Formula: see text], [Formula: see text] and [Formula: see text], with [Formula: see text] and [Formula: see text], we decide whether there exists an element [Formula: see text] with [Formula: see text] such that [Formula: see text] in [Formula: see text] time using [Formula: see text] space and report these elements in [Formula: see text] time, where [Formula: see text] is the size of the output.

DZI: An air index for spatial queries in one-dimensional channels

The wireless data broadcast environment characteristics cause the data to be delivered sequentially via one-dimensional channels. A space-filling curve has been proposed for recent wireless data broadcast environments. However, air indexing introduces various problems, including the increase in the size of the index, conversion costs, and an increase in the search space because of an inefficient structure. In this paper, we propose a distribution-based Z-order air index and query processing algorithms suitable for a wireless data broadcast environment. The proposed index organizes the object identification (hereafter called ID) hierarchically only in terms of objects that are present. We compare the proposed technique with the well-known spatial indexing technique DSI by creating equations that represent the access time and tuning time, followed by conducting a simulation-based performance evaluation. The results from experimental show that our proposed index and algorithms support efficient query processing in both range queries and K-nearest neighbor queries.

Indexingk-mers in linear space for quality value compression

Many bioinformatics tools heavily rely on -mer dictionaries to describe the composition of sequences and allow for faster reference-free algorithms or look-ups. Unfortunately, naive -mer dictionaries are very memory-inefficient, requiring very large amount of storage space to save each -mer. This problem is generally worsened by the necessity of an index for fast queries. In this work, we discuss how to build an indexed linear reference containing a set of input -mers and its application to the compression of quality scores in FASTQ files. Most of the entropies of sequencing data lie in the quality scores, and thus they are difficult to compress. Here, we present an application to improve the compressibility of quality values while preserving the information for SNP calling. We show how a dictionary of significant -mers, obtained from SNP databases and multiple genomes, can be indexed in linear space and used to improve the compression of quality value. Availability: The software is freely available at https://github.com/yhhshb/yalff.

Couchbase analytics

Couchbase Server is a highly scalable document-oriented database management system. With a shared-nothing architecture, it exposes a fast key-value store with a managed cache for sub-millisecond data operations, indexing for fast queries, and a powerful query engine for executing declarative SQL-like queries. Its Query Service debuted several years ago and supports high volumes of low-latency queries and updates for JSON documents. Its recently introduced Analytics Service complements the Query Service. Couchbase Analytics, the focus of this paper, supports complex analytical queries (e.g., ad hoc joins and aggregations) over large collections of JSON documents. This paper describes the Analytics Service from the outside in, including its user model, its SQL++ based query language, and its MPP-based storage and query processing architecture. It also briefly touches on the relationship of Couchbase Analytics to Apache AsterixDB, the open source Big Data management system at the core of Couchbase Analytics.

A heuristic approach on metadata recommendation for search engine optimization

SummaryThis study aims to recommend metadata for building a high ranking in Search Engine Result Page (SERP) by considering Search Engine Optimizations (SEO). For online marketing, it is important to place their websites on the top rank in a result of search engines. However, on‐page techniques of traditional SEO do not have logical foundation to select metadata. Metadata is an important element to prioritize of websites when search engine indexing for user queries. Thereby, for online marketing, this study proposes a method for recommending metadata, which consists of two steps: i) combining keywords and metadata from high‐ranked websites, and ii) evaluating the importance of terms based on semantic relevance. First, terms are selected with influential keywords and metadata by using their frequency and weight. Second, prioritize the terms according to semantic relevance based on a competitive learning model. We evaluated the validity of the proposed method by using three queries in Google. Experimental results demonstrate that it increases traffic of a website, by using terms, which are high‐ranked websites and semantic relevance.

An Efficient Indexing Approach for Continuous Spatial Approximate Keyword Queries over Geo-Textual Streaming Data

Current social-network-based and location-based-service applications need to handle continuous spatial approximate keyword queries over geo-textual streaming data of high density. The continuous query is a well-known expensive operation. The optimization of continuous query processing is still an open issue. For geo-textual streaming data, the performance issue is more serious since both location information and textual description need to be matched for each incoming streaming data tuple. The state-of-the-art continuous spatial-keyword query indexing approaches generally lack both support for approximate keyword matching and high-performance processing for geo-textual streaming data. Aiming to tackle this problem, this paper first proposes an indexing approach for efficient supporting of continuous spatial approximate keyword queries by integrating m i n - w i s e signatures into an AP-tree, namely AP-tree + . AP-tree + utilizes the one-permutation m i n - w i s e hashing method to achieve a much lower signature maintenance costs compared with the traditional m i n - w i s e hashing method because it only employs one hashing function instead of dozens. Towards providing a more efficient indexing approach, this paper has explored the feasibility of parallelizing AP-tree + by employing a Graphic Processing Unit (GPU). We mapped the AP-tree + data structure into the GPU’s memory with a variety of one-dimensional arrays to form the GPU-aided AP-tree + . Furthermore, a m i n - w i s e parallel hashing algorithm with a scheme of data parallel and a GPU-CPU data communication method based on a four-stage pipeline way have been used to optimize the performance of the GPU-aided AP-tree + . The experimental results indicate that (1) AP-tree + can reduce the space cost by about 11% compared with MHR-tree, (2) AP-tree + can hold a comparable recall and 5.64× query performance gain compared with MHR-tree while saving 41.66% maintenance cost on average, (3) the GPU-aided AP-tree + can attain an average speedup of 5.76× compared to AP-tree + , and (4) the GPU-CPU data communication scheme can further improve the query performance of the GPU-aided AP-tree + by 39.4%.

MapReduce‐based storage and indexing for big health data

SummaryLocality Sensitive Hashing (LSH) uses randomized method to alleviate Nearest Neighbor Search issue in high dimensional spaces. However, handling of big dataset samples for LSH algorithm becomes difficult task because of computational complexity. So, the major aim of this work is to introduce a new LSH algorithm with Hadoop MapReduce framework for enhancing proficiency of arbitrary reads over big dataset samples. The proposed Hash index improves efficiency by reducing the amount of accessing data for range queries by creating buckets based on hyperplanes. A LSH on MapReduce is developed, which decreases the random data access time among map and reduce functions, in addition, it enhances proficiency. Lastly, with the aim of validating the performance of presented index for search query in MapReduce, five performance metrics such as changing cluster size, LSH for Bucket size Balancing, the overlapped boundary of a hyperplane, Bucket creation based on the configured capacity, and non‐indexed, Hash index, and global indexed dataset on the HDFS configured capacity are utilized. The effect of these metrics on dataset on the HDFS configured capacity for the period of map and reduce functions as well depicts the pre‐eminence of the presented Hash index.