Query Language (query + language)

Distribution by Scientific Domains

Selected Abstracts

Measuring and modelling the performance of a parallel ODMG compliant object database server

Sandra de F. Mendes Sampaio
Abstract Object database management systems (ODBMSs) are now established as the database management technology of choice for a range of challenging data intensive applications. Furthermore, the applications associated with object databases typically have stringent performance requirements, and some are associated with very large data sets. An important feature for the performance of object databases is the speed at which relationships can be explored. In queries, this depends on the effectiveness of different join algorithms into which queries that follow relationships can be compiled. This paper presents a performance evaluation of the Polar parallel object database system, focusing in particular on the performance of parallel join algorithms. Polar is a parallel, shared-nothing implementation of the Object Database Management Group (ODMG) standard for object databases. The paper presents an empirical evaluation of queries expressed in the ODMG Query Language (OQL), as well as a cost model for the parallel algebra that is used to evaluate OQL queries. The cost model is validated against the empirical results for a collection of queries using four different join algorithms, one that is value based and three that are pointer based. Copyright © 2005 John Wiley & Sons, Ltd. [source]

A query language for discovering semantic associations, Part I: Approach and formal definition of query primitives

Timo Niemi
In contemporary query languages, the user is responsible for navigation among semantically related data. Because of the huge amount of data and the complex structural relationships among data in modern applications, it is unrealistic to suppose that the user could know completely the content and structure of the available information. There are several query languages whose purpose is to facilitate navigation in unknown structures of databases. However, the background assumption of these languages is that the user knows how data are related to each other semantically in the structure at hand. So far only little attention has been paid to how unknown semantic associations among available data can be discovered. We address this problem in this article. A semantic association between two entities can be constructed if a sequence of relationships expressed explicitly in a database can be found that connects these entities to each other. This sequence may contain several other entities through which the original entities are connected to each other indirectly. We introduce an expressive and declarative query language for discovering semantic associations. Our query language is able, for example, to discover semantic associations between entities for which only some of the characteristics are known. Further, it integrates the manipulation of semantic associations with the manipulation of documents that may contain information on entities in semantic associations. [source]

A query language for discovering semantic associations, Part II: sample queries and query evaluation

Timo Niemi
In our query language introduced in Part I (Niemi & Jämsen, in press) the user can formulate queries to find out (possibly complex) semantic relationships among entities. In this article we demonstrate the usage of our query language and discuss the new applications that it supports. We categorize several query types and give sample queries. The query types are categorized based on whether the entities specified in a query are known or unknown to the user in advance, and whether text information in documents is utilized. Natural language is used to represent the results of queries in order to facilitate correct interpretation by the user. We discuss briefly the issues related to the prototype implementation of the query language and show that an independent operation like Rho (Sheth et al., 2005; Anyanwu & Sheth, 2002, 2003), which presupposes entities of interest to be known in advance, is exceedingly inefficient in emulating the behavior of our query language. The discussion also covers potential problems, and challenges for future work. [source]

An expressive and efficient language for XML information retrieval

Taurai Tapiwa Chinenyanga
Several languages for querying and transforming XML, including XML-QL, Quilt, and XQL, have been proposed. However, these languages do not support ranked queries based on textual similarity, in the spirit of traditional IR. Several extensions to these XML query languages to support keyword search have been made, but the resulting languages cannot express IR-style queries such as "find books and CDs with similar titles." In some of these languages keywords are used merely as boolean filters without support for true ranked retrieval; others permit similarity calculations only between a data value and a constant, and thus cannot express the above query. WHIRL avoids both problems, but assumes relational data. We propose ELIXIR, an expressive and efficient language for XML information retrieval that extends XML-QL with a textual similarity operator that can be used for similarity joins, so ELIXIR is sufficiently expressive to handle the sample query above. ELIXIR thus qualifies as a general-purpose XML IR query language. Our central contribution is an efficient algorithm for answering ELIXIR queries that rewrites the original ELIXIR query into a series of XML-QL queries to generate intermediate relational data, and uses WHIRL to efficiently evaluate the similarity operators on this intermediate data, yielding an XML document with nodes ranked by similarity. Our experiments demonstrate that our prototype scales well with the size of the query and the XML data. [source]

EquiX,A search and query language for XML

Sara Cohen
EquiX is a search language for XML that combines the power of querying with the simplicity of searching. Requirements for such languages are discussed, and it is shown that EquiX meets the necessary criteria. Both a graph-based abstract syntax and a formal concrete syntax are presented for EquiX queries. In addition, the semantics is defined and an evaluation algorithm is presented. The evaluation algorithm is polynomial under combined complexity. EquiX combines pattern matching, quantification, and logical expressions to query both the data and meta-data of XML documents. The result of a query in EquiX is a set of XML documents. A DTD describing the result documents is derived automatically from the query. [source]

The Biomolecular Crystallization Database Version 4: expanded content and new features

Michael Tung
The Biological Macromolecular Crystallization Database (BMCD) has been a publicly available resource since 1988, providing a curated archive of information on crystal growth for proteins and other biological macromolecules. The BMCD content has recently been expanded to include 14,372 crystal entries. The resource continues to be freely available at http://xpdb.nist.gov:8060/BMCD4. In addition, the software has been adapted to support the Java-based Lucene query language, enabling detailed searching over specific parameters, and explicit search of parameter ranges is offered for five numeric variables. Extensive tools have been developed for import and handling of data from the RCSB Protein Data Bank. The updated BMCD is called version 4.02 or BMCD4. BMCD4 entries have been expanded to include macromolecule sequence, enabling more elaborate analysis of relations among protein properties, crystal-growth conditions and the geometric and diffraction properties of the crystals. The BMCD version 4.02 contains greatly expanded content and enhanced search capabilities to facilitate scientific analysis and design of crystal-growth strategies. [source]

Building secure products and solutions

Ashok K. Gupta
Many security vulnerabilities in current information technology (IT) solutions and products are the result of a piecemeal "strap-on" security approach. The inclusion of many security add-ons, such as firewalls, antivirus software, intrusion detection systems (IDSs), and intrusion prevention systems (IPSs), may imply that the security objectives were an afterthought, not adequately defined initially, or that the required security objectives were never met by the individual system components. In fact, a "grounds-up" approach to security, where each component is individually secure, in a defined network deployment scenario helps meet the need of minimal risk exposure. Security should not be bolted on; rather, it should be the prime consideration from the beginning and throughout the entire lifecycle,from concept to deployment and ongoing operation for each product in the solution. Given the ever-increasing sophistication of attacks, developing and monitoring secure products have become increasingly difficult. Despite the wide-scale awareness of common security flaws in software products, e.g., buffer overflows, resource exhaustion, and structured query language (SQL) injection, the same flaws continue to exist in some of the current products. The objective of this paper is to introduce a technology-agnostic approach to integrating security into the product development lifecycle. The approach leverages the Bell Labs Security Framework, the foundation of the International Telecommunication Union, Telecommunication Standardization Sector (ITU-T) X.805 global standard. Building this framework into the product lifecycle supports the goal of realizing secure products. The security framework can be applied to any product domain to facilitate security requirements analysis and the development of usable tools such as checklists, guidelines, and security policies. The application of Bell Labs Security Framework concepts and its use in the development of secure products are illustrated using the example of a centrally managed firewall product. © 2007 Alcatel-Lucent. [source]