Nested relations and recursive queries

The relational model is the basis for most modern databases, while SQL is the most commonly used query language. However, there are data structures and computational problems that cannot be expressed using SQL-92 queries. Among them are those concerned with the bill-of-material and corporate hierarchies. A newer standard, called the SQL-99, introduced recursive queries which can be used to solve such tasks. Yet, only recently recursive queries have been implemented in most of the leading relational databases. In this paper we have reviewed and compared implementations of the recursive queries defined by SQL:1999 through SQL:2008 and offered by leading vendors of DBMSs. Our comparison concerns features, syntax and performance.

We define a language G for querying data represented as a labeled graph G. By considering G as a relation, this graphical query language can be viewed as a relational query language, and its expressive power can be compared to that of other relational query languages. We do not propose G as an alternative to general purpose relational query languages, but rather as a complementary language in which recursive queries are simple to formulate. The user is aided in this formulation by means of a graphical interface. The provision of regular expressions in G allows recursive queries more general than transitive closure to be posed, although the language is not as powerful as those based on function-free Horn clauses. However, we hope to be able to exploit well-known graph algorithms in evaluating recursive queries efficiently, a topic which has received widespread attention recently.

The amount of sources and sheer volumes of spatiotemporal data have met an unprecedented growth during the last decade. As a consequence, a rapidly increasing number of applications are seeking to generate value by crunching those data. The development of a system that will tap into the potential value of the spatiotemporal big data analysis for a multitude of applications remains one of the biggest challenges in computer engineering. This paper delves into the key-characteristics of the most prominent suchlike systems. In particular, it provides a thorough analysis of NoSQL datastores as well as a traditional relational database system in terms of their geospatial querying capabilities.

최근 급격히 증가하는 공간 데이터를 효율적으로 처리하기 위해 많은 연구들이 진행되고 있다. 기존 관계형 데이터베이스 시스템을 확장한 공간 데이터베이스 시스템은 확장성에 대한 문제가 있으며, 분산 처리 플랫폼인 하둡을 확장한 SpatialHadoop은 중간 연산 결과를 디스크에 작성하기 때문에 파일 입출력의 오버헤드로 성능이 저하되는 문제가 있다. 본 논문은 인-메모리 기반 분산 처리 프레임워크인 스파크를 확장한 공간 연산 스파크를 제안하였다. 또한 공간 연산 스파크의 성능을 향상시키기 위하여 GPGPU를 결합한 모델을 개발하였다. 공간 연산 스파크는 중간 연산 결과를 메모리에 유지시키는 스파크의 특징을 그대로 사용하고 있으며, GPGPU 기반 공간 연산 스파크의 경우 다수의 PE를 이용하여 병렬처리하기 때문에 효율적으로 공간 연산을 수행할 수 있다. 본 논문은 단일 AMD 시스템에서 공간 연산 스파크와 GPGPU 기반 공간 연산 스파크를 구현하였다. 공간 연산 스파크와 GPGPU 기반 공간 연산 스파크의 성능을 평가하기 위하여 Point-in-Polygon 연산과 Spatial Join 연산을 수행하였으며, SpatialHadoop에 비하여 최대 8배의 성능 향상을 확인하였다. Recently, as the amount of spatial information increases, an interest in the study of spatial information processing has been increased. Spatial database systems extended from the traditional relational database systems are difficult to handle large data sets because of the scalability. SpatialHadoop extended from Hadoop system has a low performance, because spatial computations in SpationHadoop require a lot of write operations of intermediate results to the disk, resulting in the performance degradation. In this paper, Spatial Computation Spark(SC-Spark) is proposed, which is an in-memory based distributed processing framework. SC-Spark is extended from Spark in order to efficiently perform the spatial operation for large-scale data. In addition, SC-Spark based on the GPGPU is developed to improve the performance of the SC-Spark. SC-Spark uses the advantage of the Spark holding intermediate results in the memory. And GPGPU-based SC-Spark can perform spatial operations in parallel using a plurality of processing elements of an GPU. To verify the proposed work, experiments on a single AMD system were performed using SC-Spark and GPGPU-based SC-Spark for Point-in-Polygon and spatial join operation. The experimental results showed that the performance of SC-Spark and GPGPU-based SC-Spark were up-to 8 times faster than SpatialHadoop.

Path expressions have been accepted for concisely manipulating the nested structures in complex object-oriented query expressions. However, previous visual query languages hardly represent such query expressions in a concise and intuitive way partly due to improper visual representation of path expressions and partly due to lack of well-defined system and semantics of languages. In this paper, we present visual modeling of path expressions in a visual object-oriented database query language called Visual Object-Oriented Query Language (VOQL) which has excellent expressive pourer for sets, simple and intuitive syntax, and well-defined semantics. This is enabled by explicitly specifying the semantics of multi-valued path expressions based on the visual notation capable of representing set relationships in addition to functional relationships. The basic visual constructs called blobs and nested blobs denote sets of objects that path expressions represent while the constructs called binding edges and flattening edges visually simulate the notions of variable binding and dot functions in path expressions respectively. Based on the constructs, the grammar of VOQL defines the syntactic components while the semantics of query expressions are provided by syntax-directed translation to the counterparts in the extended relational calculus. Also, the visual constructs allow modeling of restricted universal quantification with a visual scoping box and effectively represent nested quantification and recursive queries without semantic ambiguities.

In this paper, we extend recent works on concrete and abstract semantics of structured query languages by considering recursive queries too. We show that combining abstraction of data and widening operators that guarantee the convergence of the computation may be useful not only for static analysis purposes, but also as a sound and effective tool for query language transformations.

Query classification in object-oriented engineering design systems

Chapter 2 - Querying

As more and more data-centric services are emerging on the Web, the diversity of APIs in this field increases rapidly. In addition to the traditional relational model, the scope of Database-as-a-Service (DaaS) products is broadened by new approaches, such as the more lenient key-value stores. Many DaaS APIs address the same concepts, making them incompatible with each other, yet not fundamentally different. In this paper, we address this issue by drafting a concept for a "universal" API for DaaS systems based on the REST architectural style. The new API is universal in the sense that it is aimed to be suitable for DaaS systems ranging from those that allow storage of schema-less data to systems with the capabilities of a traditional relational database system. After the presentation of the concept, we critically review it, revealing general problems of such a universal API, and point out a more promising path for future work.

Nowadays, ontologies are used in several research domains by offering the means to describe and represent concepts of information sources. Therefore, several approaches and systems storing ontologies and their instances in the same repository (database) have been proposed. As a consequence, defining a query language to support ontology-based database (OBDB) becomes a challenge for the database community. In this paper, we present OntoQL, an ontology query language for OBDBs. Firstly, we present formally the OBDB data model supported by this language. Secondly, an overview of the algebra defining the semantics of operators used in OntoQL is described. Several query examples showing the interest of this language compared to traditional database query languages are given along this paper. Finally, we present a prototype of the implementation of OntoQL.

Interaction with geographic information systems via spatial queries

The main subject of this monograph is a reconstruction of the history of deposition and facial development of Upper Jurassic and Lower Cretaceous deposits in the basement of the Carpathian Foredeep, based on data available from boreholes and a 3D seismic survey. The research area is located in the central part of the Carpathian Foreland, between two cities: Dąbrowa Tarnowska in the north-west and Dębica in the south-east. The new 3D seismic survey made in 2015 and the O-1 deep borehole – drilled in the same year and portraying a full profile of the Mesozoic sediments – allowed for much better recognition and documentation of many details of the geological structure of this previously poorly mapped area. The sedimentation of the carbonate formations of the Carpathian Foreland during the Late Jurassic and the Early Cretaceous took place in the shelf zone of the northern, passive margin of the Tethys Ocean. A characteristic feature of the Upper Jurassic sediments is their high facies diversity, due mainly to the presence of biohermal complexes and sets of layered marly-limestone sediments. Chapter 2 presents the geological structure of all structural stages in the area under study, including the lithological development, the lithostratigraphic divisions applied, and the regional palaeogeographic frameworks. Chapter 3 discusses both the history of research and the current state of knowledge regarding the Upper Jurassic and Lower Cretaceous carbonate sediments of the Carpathian Foreland. Chapter 4 describes the lithological characteristics of the carbonate sediments, considering lithostratigraphic units. This characterisation is based on a macroscopic examination of the available core material and analysis of the well logs. The lithostratigraphic profiles of selected deeper boreholes from the research area and its close vicinity document the current state of knowledge on lithostratigraphy and the facies development of the Upper Jurassic and Lower Cretaceous deposits. Chapter 5 features the microfacies and micropalaeontological characteristics of the carbonate sediments under study. Based on the results of many years of research and literature data, the possibilities of determining the age of every lithostratigraphic unit are discussed. Chapter 6 presents the analysis of the seismic 3D image based on selected seismic attributes. As part of the work, the following attributes are discussed: RMS Amplitude, Envelope, Instantaneous phase, Dominant frequency, Instantaneous bandwidth, Apparent polarity, Relative acoustic impedance, First derivative, Iso-frequency component, Time gain, Chaos, Variance (Edge method), and Local flatness. The analysis revealed additional important information regarding both the lithological development and the spatial range of sediments of individual lithostratigraphic units, at the same time facilitating the detailed location of fault zones. Based on the interpretation of the seismic image within the studied rock complex, the occurrence of angular unconformity, disturbance, and deformation zones related to synsedimentary tectonic as well as probable gravity-flow deposits are also documented. Chapter 7 presents lithofacial cross-sections constructed along selected seismic sections reflecting the spatial distribution and relationships between the sediments of individual lithostratigraphic units. Chapter 8 analyses the distribution of Upper Jurassic biohermal complexes in relation to the morphology of the Jurassic base surface. An analysis of the distribution of organic buildups belonging to the Huge Sponge-Microbial Bioherms Series, interpreted indirectly from seismic image, indicates two main areas where they can be found. These are the north-west part of the study area – where a quite extensive biohermal complex occurs (‘Complex N’), the exact range of which is difficult to determine due to later regional dolomitisation processes – and the area located in the central part of the seismic survey, where a complex of several very tall buildups with steep edges was found (‘Complex S’). Chapter 9 is devoted to the issue of the depositional history of the Late Jurassic–Early Cretaceous sedimentary basin of the Carpathian Foreland and to a discussion of the role of the most important factors influencing facies distribution in the research area. It has been shown that a characteristic feature of a large part of the Jurassic sediments is the strongly diachronic nature of the distribution of facies controlled by the varying bottom relief of the sedimentation basin and by some local factors related to synsedimentary tectonic episodes. The Sponge-Globuligerinid Series, beginning the profile of the Upper Jurassic sediments and representing the deepest sedimentation stage in the open shelf conditions, is characterised by a relatively high homogeneity of lithology in the whole Carpathian Foreland area. The ‘S’ biohermal complex developed over the elevated zone composed of several smaller tectonic elements, whilst the ‘N’ biohermal complex developed on a large, elevated part of the horst zone. The intensively developing ‘N’ and ‘S’ biohermal complexes affected successive deposition of the Late Jurassic sedimentary basin in the study area more and more. Those biohermal complexes were the source of the material redeposited into deeper parts of the sedimentary basin. On seismic profiles in the south-east neighbourhood of the ‘S’ biohermal complex, there is a characteristic high-amplitude record including the entire reflection set of variable dip angles. The frequent polarity changes which are visible within this zone in the Apparent polarity attribute, as well as the extremely variable range of values the Relative acoustic impedance attribute, prove the strong lithological differentiation of this rock complex. During the Tithonian time (sedimentation of the Coral-Oncolite Series), there was clear unification of the sedimentation conditions in the entire Carpathian Foreland area, mainly due to disappearance of the bottom relief diversity. At the same time another stage of dislocation reactivation occurred, as evidenced by the angular unconformity and the erosion traces of older sediments associated with this unconformity. The deposits of the Lower Shellbed-Oolite Series scattered throughout the research area represent various types of shallow-water sedimentation environments (including tidal, lagoon, and barrier zones) that developed in the Carpathian Foreland area on the borderline between the Late Jurassic and the Early Cretaceous. The sedimentation environment of the Marly-Shellbed Series dated to the Berriasian can be described as extremely shallow-water, with lagoon facies and under the influence of brackish environments. The sediments of the last two series of the Lower Cretaceous (i.e. the Mudstone-Limestone and Upper Shellbed-Oolite Series) represent the shallow-marine facies associated with marine transgression that took place during the Valanginian. The processes that have had the greatest impact on the current character and preservation of the rock series under study can be pinpointed and a comprehensive characterisation of these formations can be undertaken thanks to the depositional history of the Late Jurassic – Early Cretaceous sedimentary basin of the Carpathian Foreland presented herein, the macroscopic examination of the available core material, the microfacial and micropalaeontological analysis of individual lithostratigraphic units, and the interpretation of the seismic image. Keywords: Jurassic, Cretaceous, lithofacies, lithostratigraphy, biostratigraphy, seismic interpretation, seismic attributes

The National Children's Research Centre (NCRC), the single largest paediatric research centre in Ireland, has been in existence for over 50years and is located on the grounds of the largest children's hospital in Ireland; Children's Health Ireland at Crumlin. Professor Puri was appointed as the Director of the Research in 1989 and became President of the NCRC in 2009, a position he held until 2016. Professor Puri is one of the most cited paediatric surgical researchers in the world. His research work has been cited over 23,500 times in peer-reviewed articles with an h-index of 76 and i10-index of 494. The aim of this review is to analyse the most relevant areas of academic research at the NCRC, Dublin, during the years when Prof. Puri was Director/President of the NCRC. In addition, the relevant factors essential to create a successful paediatric surgical research centre will be discussed. A literature search using PubMed/Medline was carried out using the search terms "Prem Puri" over a 40-year period (1980-2020). Articles were analysed to identify the most significant research areas in the field of paediatric surgical research and the relevant laboratory and clinical findings. In addition, a separate analysis of successful funding and human factors, such as research fellows working at the NCRC, was also carried out. During the period under review, Professor Puri's team published 750 articles in peer-reviewed journals. Three main areas of research were reviewed with a total number of 391 articles: congenital diaphragmatic hernia (CDH) was the topic with the largest number of publications (153), followed by Hirschsprung's disease (HSCR) (144) and Vesicoureteral reflux (VUR) (94). Eighty research fellows, all paediatric surgeons, from 18 different countries were trained in basic science under the supervision of Professor Puri at the NCRC. Over the last three decades, the NCRC has been one of the most successful centres for paediatric surgical research in the world. The three areas of research with the largest number of publications were identified as CDH, HSCR and VUR. Various factors can explain the success of the NCRC: (a) the constant presence, for over 30years, of a very successful paediatric surgeon leading the centre, (b) a multicultural laboratory with research fellows from all over the world and (c) grants of more than 15million raised over the years, which guaranteed a constant flow of resources for laboratory research.

The article defines the current state and dynamics of the scientific cooperation between Russia and non-Baltic post-Soviet states by studying researchers’ scientific co-publications indexed in the Web of Science. The statistics on the number of Russian and post-Soviet authors’ bilateral scientific articles in 2000–2017 were analyzed, as well as distribution of the articles by publication year, area of research, main sponsors, and authors’ organizational affiliations. Four groups of countries were specified, for which the dynamics of scientific publication cooperation with Russia can be described as growing, positive, stagnating, and dwindling respectively. The main areas of scientific cooperation between Russia and post-Soviet states were identified in general and for each partner country in particular, as well as the leading cooperating organizations, key areas of joint research, and major research sponsors. The comparative relevance of co-publications for the scientific community was evaluated through scientific citation indexes for each post-Soviet partner country and each key area of research. The valuable role of higher education institutions in maintaining scientific cooperation in the context of adverse political and economic environments was specified.

The Brazilian population in the United States (U.S.), a Latinx subgroup, is rapidly growing and aging but remains underrepresented in U.S. health research. In addition to group-specific genetic and environmental risks, Brazilian immigrants and their offspring in the U.S. likely have cumulative risks for health inequities.It is estimated that 71% of Brazilian immigrants in the U.S. are undocumented, which may limit healthcare access/utilization. Furthermore, mental health is reported as a health priority by Brazilian immigrants in the U.S., and there is a lack of research on Alzheimer's disease and related dementia (AD/ADRD) in this population. We reviewed the scientific literature using traditional (e.g., PubMed) sources and databases generated by U.S. and Brazilian governments, as well as international organizations, and press articles. This perspective review lists recommendations for researchers, health providers, and policymakers to promote greater inclusion of U.S. Brazilian populations in health research and care. The review identifies research areas in need of attention to address health inequities and promote mental/brain health in Brazilian immigrants and their offspring living in the U.S. These research areas are: 1) epidemiological studies to map the prevalence and incidence of mental/brain health conditions; 2) research on aging and AD/ADRD risk factors among Brazilian populations in the U.S.; and 3) the need for greater representation of U.S-residing Brazilian population in other relevant research areas involving genetics, neuropathology, and clinical trials. The recommendation and research efforts proposed should help to pave the way for the development of community-engagement research and to promote mental/brain health education, improvement of mental/brain health and AD/ADRD services, and the development of culturally-informed intervention to the U.S.-residing Brazilian communities. The Brazilian population in the United States is growing but is underrepresented in U.S. health research.Approximately 71% of Brazilian immigrants in the United States are undocumented, with an increased risk for health inequities.Mental health is reported as a central health priority by Brazilian immigrants in the United States.There is a lack of research on Alzheimer's disease and other dementias (ADRD) in Brazilian immigrants in the United States.Epidemiological research is needed to map the prevalence/incidence of mental health conditions and ADRD risk factors among Brazilian immigrants in the United States.