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Anatomy of a Native XML Base Management System
- VLDB JOURNAL
, 2002
"... Several alternatives to manage large XML document collections exist, ranging from file systems over relational or other database systems to specifically tailored XML repositories. In this paper we give a tour of Natix, a database management system designed from scratch for storing and processing XML ..."
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Cited by 93 (29 self)
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Several alternatives to manage large XML document collections exist, ranging from file systems over relational or other database systems to specifically tailored XML repositories. In this paper we give a tour of Natix, a database management system designed from scratch for storing and processing XML data. Contrary
XMLTM: High-Performance XML Extensions for Commercial Database Systems
, 2002
"... Due to the success of XML for data interchange, relational database products now include support for processing of XML data. A common approach, subsequently referred to as XML extensions, stores XML documents in characterlarge-object (CLOB) attributes and extends the database engine with XML-specifi ..."
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Cited by 1 (0 self)
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Due to the success of XML for data interchange, relational database products now include support for processing of XML data. A common approach, subsequently referred to as XML extensions, stores XML documents in characterlarge-object (CLOB) attributes and extends the database engine with XML-specific functionality to read and update these attributes. In addition, XML extensions materialize views on XML content in so-called side tables. Triggers guarantee consistency of documents and view materializations. However, a series of preliminary experiments with XML extensions has revealed that performance of concurrent queries and updates is low. This motivates to design XML extensions more carefully, aiming at better performance. This study identifies two important shortcomings of XML extensions: (1) Database lock contention hinders parallelism unnecessarily. (2) Querying and updating of an XML document requires to load the entire document into an internal representation. We propose a solution that addresses these problems as follows: Its core is a transaction manager XMLTM. It features a new locking protocol DGLOCK. DGLOCK generalizes the protocol for locking on directed acyclic graphs for XML data. XMLTM allows to run XML processing at low ANSI isolation degrees and to release database locks early without sacrificing correctness. Regarding the second problem, we make use of the idea of decomposing XML documents into fragments. The rationale is that the internal representation is generated only for the relevant fragments. We have implemented our solution on top of the XML Extender for IBM DB2. Our experimental evaluation shows that our approach consistently yields performance improvements by an order of magnitude.
Transaction Isolation In the Sedna Native XML DBMS
, 2004
"... XML has become the most important technique to exchange data in World Wide Web. As consequence, an interest to native XML databases has surfaced. Concurrency control methods for traditional databases are not adequate for XML databases, because they do not capture the specific of XML data model. In t ..."
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XML has become the most important technique to exchange data in World Wide Web. As consequence, an interest to native XML databases has surfaced. Concurrency control methods for traditional databases are not adequate for XML databases, because they do not capture the specific of XML data model. In this paper we propose a locking mechanism, developed in Sedna, which allows to achieve a high degree of concurrency and takes into account the properties of structural and manipulation parts of XML model.
Tools for XML-based Maintenance of Heterogeneous Software
"... Abstract. The paper presents research results related to an ongoing European IST project called MECASP (Maintenance and improvement of componentbased applications diffused in ASP mode), aiming at developing a set of tools for tracking the evolution of heterogeneous software (built using heterogeneou ..."
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Abstract. The paper presents research results related to an ongoing European IST project called MECASP (Maintenance and improvement of componentbased applications diffused in ASP mode), aiming at developing a set of tools for tracking the evolution of heterogeneous software (built using heterogeneous development tools, such as Java IDEs, relational DBMSs, CASE tools, document editors etc). MECASP cannot benefit from existing version management tools like CVS or Microsoft VSS because these tools deal with versioning text files only and have a primitive mechanism for change tracking and version merge. The paper first presents the XML-based solution for software modeling in MECASP. Then, the basic platform and the general architecture of MECASP are given, along with the limits of the existing open source software for the implementation of the XML repository manager, the core of MECASP. The paper also presents the specific features of the MECASP browser, conversion tools and merger. 1
ABSTRACT XMLTM: Efficient Transaction Management for XML Documents
"... A common approach to storage and retrieval of XML documents is to store them in a database, together with materialized views on their content. The advantage over ”native” XML storage managers seems to be that transactions and concurrency are for free, next to other benefits. But a closer look and pr ..."
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A common approach to storage and retrieval of XML documents is to store them in a database, together with materialized views on their content. The advantage over ”native” XML storage managers seems to be that transactions and concurrency are for free, next to other benefits. But a closer look and preliminary experiments reveal that this results in poor performance of concurrent queries and updates. The reason is that database lock contention hinders parallelism unnecessarily. We therefore investigate concurrency control at the semantic, i.e., XML level and describe a respective transaction manager XMLTM. It features a new locking protocol DGLOCK. It generalizes the protocol for locking on directed acyclic graphs by adding simple predicate locking on the content of elements, e.g., on their text. Instead of using the original XML documents, we propose to take advantage of an abstraction of the XML document collection known as DataGuides. XMLTM allows to run XML processing at the underlying database at low ANSI isolation degrees and to release database locks early without sacrificing correctness in this setting. We have built a complete prototype system that is implemented on top of the XML Extender for IBM DB2. Our evaluation shows that our approach consistently yields performance improvements by an order of magnitude. We stress that our approach can also be implemented within a native XML storage manager, and we expect even better performance.
Software Maintenance Based on Versioned XML Models
"... Abstract: The paper presents the framework and the main tools for software maintenance (i.e creation and management of versions), developed during the IST project called MECASP (Maintenance and improvement of component-based applications diffused in ASP mode). The specific features and general archi ..."
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Abstract: The paper presents the framework and the main tools for software maintenance (i.e creation and management of versions), developed during the IST project called MECASP (Maintenance and improvement of component-based applications diffused in ASP mode). The specific features and general architecture of MECASP, given at the beginning of the paper, make it differ from the existing (open source and commercial) products for version management. The paper gives a brief description of the software architecture in MECASP, represented by XML meta-models and versioned models. Also, it presents the basic components of the specific browser in MECASP. Among the problems to be solved for the implementation of MECASP (most of them from scratch), the paper emphasizes the issues for the implementation of an open source-based XML repository manager and of a rule-based and semantically enhanced merge strategy, devoted to the maintenance of heterogeneous types of software. The use of MECASP for software maintenance and adaptation is exemplified by the use cases given at the end of the paper, for both software design and deployment phases.
