Composite-object views in relational DBMS: an implementation perspective

We present a novel approach for supporting Composite Objects (CO) as an abstraction over the relational data. This approach brings the advanced CO model to existing relational databases and applications, without requiring an expensive migration to other DBMSs which support CO. The concept of views in relational DBMSs (RDBMS) gives the basis for providing the CO abstraction. This model is strictly an extension to the relational model, and it is fully upward compatible with it. We present an overview of the data model. We put emphasis in this paper on showing how we have made the extensions to the architecture and implementation of an RDBMS (Starburst) to support this model. We show that such a major extension to the data model is in fact quite attractive both in terms of implementation cost and query performance. We introduce a CO cache for navigation through components of a CO. With this technique, the performance of navigation through COs, which has been of a concern in RDBMSs in the past, is in fact quite satisfactory. We present our practical experience in using this facility. We show that our work on CO enables existing RDBMSs to incorporate efficient CO facilities at a low cost and at a high degree of application reusability and database sharability

Integration of composite objects into relational query processing : the SQL/XNF approach

Complex database applications, such as design applications, multi-media and AI applications, and even enhanced business applications can benefit significantly from a database language that supports composite objects. The data used by such applications are often shared with more traditional applications, such as cost accounting, project management, etc. Hence, sharing of the data among traditional applications and complex object applications is important. Our approach, called SQL Extended Normal Form (short SQL/XNF) provides a general framework that supports novel processing models based on composite objects. Especially, it enhances relational technology by a composite object facility, which comprises not only extraction of composite objects from a shared database, but also adequate browsing and manipulation facilities provided by an appropriate application programming interface

Rules for query rewrite in native XML databases

In recent years, the database community has seen many sophisticated Structural Join and Holistic Twig Join algo-rithms as well as several index structures supporting the evaluation of twig query patterns. Even though almost all XML query evaluation proposals in the literature use one of those evaluation methods, we believe that (1) there is no internal representation that enables a smooth transition between the XQuery language level and physical algebra operators, and (2) there is still no approach that consid-ers the combination of content-and-structure indexes, Struc-tural Join, and Holistic Twig Join algorithms to speed up the evaluation of twig queries. To overcome this deficit, we propose an enhancement to Starburst’s Query Graph Model as an internal representation for XML query languages such as XQuery. This representation permits the usage of simple (binary) join operators—such as Structural Joins—and com-plex (n-way) join operators—such as Holistic Twig Joins— as part of the logical algebra. For twig queries, we define a set of rewrite rules which initiate query graph transforma-tions towards improved processability, e. g., to fuse adjacent binary join operators to a complex join operator. To en-hance the evaluation flexibility of twig queries, we come up with further rewrite rules to prepare query graphs—even be-fore query transformation—for making the most of existing joins and indexes. 1

Physical Data Independence, Constraints and Optimization with Universal Plans

We present an optimization method and al gorithm designed for three objectives: physi cal data independence, semantic optimization, and generalized tableau minimization. The method relies on generalized forms of chase and backchase with constraints (dependen cies). By using dictionaries (finite functions) in physical schemas we can capture with con straints useful access structures such as indexes, materialized views, source capabilities, access support relations, gmaps, etc. The search space for query plans is defined and enumerated in a novel manner: the chase phase rewrites the original query into a universal plan that integrates all the access structures and alternative pathways that are allowed by appli cable constraints. Then, the backchase phase produces optimal plans by eliminating various combinations of redundancies, again according to constraints. This method is applicable (sound) to a large class of queries, physical access structures, and semantic constraints. We prove that it is in fact complete for path-conjunctive queries and views with complex objects, classes and dictio naries, going beyond previous theoretical work on processing queries using materialized views

Метод автоматичної зовнішньої оптимізації sql-запитів в умовах невизначеності фізичної та логічної структури бази даних

The paper deals with factors affecting on the  data accessing speed in information systems. A method of automatic external SQL-query optimization is presented, it is based on the local model of the controlled process, and it makes the optimization of the SQL-queries regardless of the used database management system and its settings. Structural and functional diagram of the adaptive system of the external SQL-query optimization is presented.В работе рассмотрены факторы, влияющие на скорость получения информации в информационных системах. Изложен метод автоматической внешней оптимизации SQL-запросов на основе локальной модели управляемого процесса, который позволяет проводить оптимизацию SQL-запросов независимо от применяемой системы управления базами данных и ее настроек. Представлена ​​структурно-функциональная схема адаптивной системы внешней оптимизации SQL-запросов.В роботі розглянуто фактори, які впливають на швидкість отримання інформації в інформаційних системах. Викладено метод автоматичної зовнішньої оптимізації SQL-запитів на основі локальної моделі керованого процесу, який дозволяє проводити оптимізацію SQL-запитів незалежно від застосованої системи керування базами даних та її налаштувань. Представлена структурно-функціональна схема адаптивної системи зовнішньої оптимізації SQL-запитів