On distributed data processing in data grid architecture for a virtual repository

The article describes the problem of integration of distributed, heterogeneous and fragmented collections of data with application of the virtual repository and the data grid concept. The technology involves: wrappers enveloping external resources, a virtual network (based on the peer-topeer technology) responsible for integration of data into one global schema and a distributed index for speeding-up data retrieval. Authors present a method for obtaining data from heterogeneously structured external databases and then a procedure of integration the data to one, commonly available, global schema. The core of the described solution is based on the Stack-Based Query Language (SBQL) and virtual updatable SBQL views. The system transport and indexing layer is based on the P2P architecture

CRUD-DOM: a model for bridging the gap between the object-oriented and the relational paradigms

Best Paper AwardObject-oriented programming is the most successful programming paradigm. Relational database management systems are the most successful data storage components. Despite their individual successes and their desirable tight binding, they rely on different points of view about data entailing difficulties on their integration. Some solutions have been proposed to overcome these difficulties, such as Embedded SQL, object/relational mappings (O/RM), language extensions and even Call Level Interfaces (CLI), as JDBC and ADO.NET. In this paper we present a new model aimed at integrating object-oriented languages and relational databases, named CRUD Data Object Model (CRUD-DOM). CRUDDOM relies on CLI (JDBC) and aims not only at exploring CLI advantages as preserving its performance and SQL expressiveness but also on providing a typestate approach for the implementation of the ResultSet interface. The model design aims to facilitate the development of automatic code generation tools. We also present such a tool, called CRUD Manager (CRUD-M), which provides automatic code generation with a complementary support for software maintenance. This paper shows that CRUD-DOM is an effective model to address the aforementioned objectives.(undefined

An object query language for multimedia federations

The Fischlar system provides a large centralised repository of multimedia files. As expansion is difficult in centralised systems and as different user groups have a requirement to define their own schemas, the EGTV (Efficient Global Transactions for Video) project was established to examine how the distribution of this database could be managed. The federated database approach is advocated where global schema is designed in a top-down approach, while all multimedia and textual data is stored in object-oriented (O-O) and object-relational (0-R) compliant databases. This thesis investigates queries and updates on large multimedia collections organised in the database federation. The goal of this research is to provide a generic query language capable of interrogating global and local multimedia database schemas. Therefore, a new query language EQL is defined to facilitate the querying of object-oriented and objectrelational database schemas in a database and platform independent manner, and acts as a canonical language for database federations. A new canonical language was required as the existing query language standards (SQL: 1999 and OQL) axe generally incompatible and translation between them is not trivial. EQL is supported with a formally defined object algebra and specified semantics for query evaluation. The ability to capture and store metadata of multiple database schemas is essential when constructing and querying a federated schema. Therefore we also present a new platform independent metamodel for specifying multimedia schemas stored in both object-oriented and object-relational databases. This metadata information is later used for the construction of a global schemas, and during the evaluation of local and global queries. Another important feature of any federated system is the ability to unambiguously define database schemas. The schema definition language for an EGTV database federation must be capable of specifying both object-oriented and object-relational schemas in the database independent format. As XML represents a standard for encoding and distributing data across various platforms, a language based upon XML has been developed as a part of our research. The ODLx (Object Definition Language XML) language specifies a set of XMLbased structures for defining complex database schemas capable of representing different multimedia types. The language is fully integrated with the EGTV metamodel through which ODLx schemas can be mapped to 0-0 and 0-R databases

A New Rational Algorithm for View Updating in Relational Databases

The dynamics of belief and knowledge is one of the major components of any autonomous system that should be able to incorporate new pieces of information. In order to apply the rationality result of belief dynamics theory to various practical problems, it should be generalized in two respects: first it should allow a certain part of belief to be declared as immutable; and second, the belief state need not be deductively closed. Such a generalization of belief dynamics, referred to as base dynamics, is presented in this paper, along with the concept of a generalized revision algorithm for knowledge bases (Horn or Horn logic with stratified negation). We show that knowledge base dynamics has an interesting connection with kernel change via hitting set and abduction. In this paper, we show how techniques from disjunctive logic programming can be used for efficient (deductive) database updates. The key idea is to transform the given database together with the update request into a disjunctive (datalog) logic program and apply disjunctive techniques (such as minimal model reasoning) to solve the original update problem. The approach extends and integrates standard techniques for efficient query answering and integrity checking. The generation of a hitting set is carried out through a hyper tableaux calculus and magic set that is focused on the goal of minimality.Comment: arXiv admin note: substantial text overlap with arXiv:1301.515

CRUD-DOM: a model for bridging the gap between the object-oriented and the relational paradigms : an enhanced performance assessment based on a case study

The development of database applications comprises three different tiers: application tier, database tier and finally the middle tier also known as the data access layer. The development of each tier per-se entails many challenges. Very often the most difficult challenges to be addressed derive from non-functional requirements, as productivity, usability, performance, reliability, high-availability and transparency. This paper is focused on defining and presenting a model for the data access layer aimed to integrate object-oriented application tiers and relational database tiers. The model addresses situations on which users need to explicitly write down complex static CRUD expressions and simultaneously get advantages regarding some non-functional requirements. The model, known as CRUD Data Object Model (CRUD-DOM), tackles the following non-functional requirements: performance, usability and productivity. The main contributions of this paper are threefold: 1) to present an extended model of CRUD-DOM; 2) to carry out an extended performance assessment based on a case study; 3) to present a tool, called CRUD Manager (CRUD-M), which provides automatic code generation with complementary support for software test and maintenance. The main outcome from this paper is the evidences that the pair CRUD-DOM and CRUD-M effectively addresses productivity, performance and usability requirements in the aforementioned context

a(MDÆ)2: A Model Driven Approach to Multi-Dimensional Separation of Concerns with OCL

AbstractA typical activity in the object-oriented software engineering process involves the construction of a class structure in terms of which the system behaviour is to be specified. The behaviour, however, commonly consists of multiple tasks, each of which usually needs only part of the information available in that class structure. Additionally, a different representation of the required information may be appropriate. Therefore, it would be useful to be able to have multiple views on the global class structure, each being suitable for the specification of the behaviour related to a certain task. This paper introduces a(MDÆ)2, a technique to realise such a strategy. It incorporates OCL as a powerful query language and advocates a model driven development process which relieves the developer from the burden of manually writing a considerable amount of tedious and error-prone code

PySBQL – Python-like query language constructed using stack base approach

PySBQL (Python-like Stack Based Query Language) is a full scale programming and querylanguage. Its syntax is based upon the Python’s syntax, which makes PySBQL highly readable andeasy to use. Contrary to the classical approach in query languages, semantics is defined using acommon structure for programming languages – the Environment Stack (ENVS). As a querylanguage it is similar to SBQL proposed by Subieta [1,2]. The PySBQL language is implementedin Monad – Object Oriented Database Management System