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DBPQL: An Integrated Database Programming and Query Language for Distributed Object Bases
"... Database systems are an indispensable tool in most information science applications. They are extensively used within business information systems, web-based information services, on-line teaching systems, genome databases, etc. ..."
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Database systems are an indispensable tool in most information science applications. They are extensively used within business information systems, web-based information services, on-line teaching systems, genome databases, etc.
Towards Algebraic Query Optimisation
"... XML-based databases have become a major area of interest in database research. Abstractly speaking they can be considered as a resurrection of complex-value databases using constructors for records, lists, unions plus optionality and references. XQuery has become the standard query language for XML. ..."
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XML-based databases have become a major area of interest in database research. Abstractly speaking they can be considered as a resurrection of complex-value databases using constructors for records, lists, unions plus optionality and references. XQuery has become the standard query language for XML. As XQuery is a declarative query language, the problem of query optimisation arises. In this paper an algebraic approach to query optimisation is introduced. This is based on a translation of XQuery into a query algebra for rational tree types. The algebra uses simple operations on types and structural recursion for lists. The translation exploits linguistic reflection for the type-safe expansion of path expressions. The availability of an algebraic representation of queries permits query rewriting, which in combination with cost heuristics permits queries to be rewritten and thus optimised.
AN OVERVIEW OF THE OBJECT-ORIENTED DATABASE PROGRAMMING LANGUAGE DBPQL
"... Abstract: In this paper, we present a new approach to the integration of object-oriented programming languages, database programming languages and query languages. While object-oriented programming languages and languages that are supported by object database systems appear to be closely related, th ..."
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Abstract: In this paper, we present a new approach to the integration of object-oriented programming languages, database programming languages and query languages. While object-oriented programming languages and languages that are supported by object database systems appear to be closely related, there are a number of significant differences that affect language design and implementation. Such issues include the degree of encapsulation, persistence, the incooperation types and classes, inheritance, concurrency,NULL values, garbage collection etc. In this paper, we outline the respective challenges that affect language design and provide a brief overview of the integrated object-oriented database programming and querying language DBPQL. 1
METADATA QUALITY ISSUES IN LEARNING REPOSITORIES
, 2013
"... Metadata lies at the heart of every digital repository project in the sense that it defines and drives the description of digital content stored in the repositories. Metadata allows content to be successfully stored, managed and retrieved but also preserved in the long-term. Despite the enormous imp ..."
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Metadata lies at the heart of every digital repository project in the sense that it defines and drives the description of digital content stored in the repositories. Metadata allows content to be successfully stored, managed and retrieved but also preserved in the long-term. Despite the enormous importance of metadata in digital repositories, one that is widely recognized, studies indicate that what is defined as metadata quality, is relatively low in most cases of digital repositories. Metadata quality is loosely defined as “fitness for purpose” meaning that low quality of metadata means that metadata cannot fulfill its purpose which is to allow for the successful storage, management and retrieval of resources. In practice, low metadata quality leads to ineffective searches for content, ones that recall the wrong resources or even worse, no resources which makes them invisible to the intended user, that is the “client” of each digital repository. The present dissertation approaches this problem by proposing a
DBAA/ACL- A DATABASE AGENT ARCHITECTURE AND COMMUNICATION LANGUAGE ABSTRACT
"... Reliable support for distributed data management is one of the key features of present and future database systems. In this paper, we propose an agent-based communication mechanism for distributed database systems. First, an agent architecture (DBAA) is introduced. Agents can function on their own o ..."
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Reliable support for distributed data management is one of the key features of present and future database systems. In this paper, we propose an agent-based communication mechanism for distributed database systems. First, an agent architecture (DBAA) is introduced. Agents can function on their own or work cooperatively with a (virtual) collection, block or federation of agents. While working towards a certain goal, agents may exploit concurrency, parallelism and distribution. To do so, communication capabilities are required. Thus, a corresponding agent communication language, DBACL, is proposed. DBACL supports a variety of communication types (i.e. one-to-one, one-to-many and broadcast), message transfer modes (e.g. streams), and message types (e.g. signals, notifications, requests, and negotiations). Besides efficiency and interoperability, simplicity has been another main objective underlying our research.
Using Reflection for Querying XML Documents
- In Database Technology – Proceedings ADC 2006
"... XML-based databases have become a major area of interest in database research. Abstractly speaking they can be considered as a resurrection of complexvalue databases using constructors for records, lists, unions plus optionality and references. XQuery has become the standard query language for XML. ..."
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XML-based databases have become a major area of interest in database research. Abstractly speaking they can be considered as a resurrection of complexvalue databases using constructors for records, lists, unions plus optionality and references. XQuery has become the standard query language for XML. In this paper an implementation of XQuery based on linguistic reflection is proposed. That is, XQuery is translated into a query algebra for rational tree types based on simple operations and structural recursion for lists. The major purpose of using reflection is to expand path expressions in a type-safe way.
Acta Cybernetica 19 (2010) 765–805. A Customised ASM Thesis for Database Transformations
"... In order to establish a theoretical foundation for database transforma-tions, we search for a universal computation model as an umbrella for queries and updates. As updates are fundamentally distinct from queries in many re-spects, computation models for queries cannot be simply extended to database ..."
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In order to establish a theoretical foundation for database transforma-tions, we search for a universal computation model as an umbrella for queries and updates. As updates are fundamentally distinct from queries in many re-spects, computation models for queries cannot be simply extended to database transformations. This motivates the question whether Abstract State Ma-chines (ASMs) can be used to characterise database transformations in gen-eral. In this paper we start examining the differences between database trans-formations and algorithms, which give rise to the formalisation of five postu-lates for database transformations. Then a variant of ASMs called Database Abstract State Machines (DB-ASMs) is developed, and we prove that DB-ASMs capture database transformations, i.e. the main result of the paper is that every database transformation stipulated by the postulates can be behaviourally simulated by a DB-ASM.
