Mahesh B Chaudhari

LINQ ROX!: integrating LINQ into the database curriculum

The Language INtegrated Query (LINQ) language is a declarative query language integrated within an object-oriented programming language that provides a unified paradigm for querying relations, objects, and XML (ROX). This paper describes a suite of exercises, from cooperative in-class activities to larger-scale graded assignments, for incorporating LINQ into the database curriculum. These exercises support various student learning outcomes and illustrate the applicability of LINQ by querying the same database enterprise across the ROX data models.

Detecting common subexpressions for multiple query optimization over loosely-coupled heterogeneous data sources

The research presented in this paper supports the identification of common subexpressions as candidates for potential materialized views that form the basis of multiple query optimization in a loosely-coupled distributed system where query expressions access heterogeneous data sources, including relations and data-centric XML. This paper introduces a unifying mixed multigraph formalism to represent SQL, XQuery, and LINQ queries in a common query graph model and a heuristics-based algorithm to detect common subexpressions. The identified common subexpressions represent an opportunity for defining a materialized view to avoid repeating computation. The common subexpressions may access only relations, only XML, or a combination of relations and XML. The mixed multigraph model and the heuristic rules presented in this paper have distinguished advantages over the existing approaches that consider only relational or XML data sources individually. The mixed multigraph model can present SQL, XQuery, and LINQ queries in a single graph model and the heuristic rules are designed to consider the identical and subsumed conditions at the same time. A prototype implementation of the algorithm illustrates the applicability of the approach using various examples from the research literature as well as scenarios over a Criminal Justice enterprise that include common subexpressions across relational and XML data sources.

Towards a hybrid relational and XML benchmark for loosely-coupled distributed data sources

Designed heterogeneous data sources for a hybrid version of the TPC-H enterprise.Developed hybrid LINQ queries over the relational and XML data sources.Evaluated the hybrid benchmark for loosely-coupled distributed data sources.Assessed query performance for two database products with various options. There are known benchmarks for the performance evaluation of relational and XML databases. However, there is an increasing demand for database applications that require access to heterogeneous loosely-coupled distributed data sources. This paper presents a hybrid benchmark based on TPC-H where the data sources are heterogeneous. Specifically, the paper describes the design of the relational and XML data sources as well as the query redesign in the LINQ query language, which supports queries over heterogeneous data sources. The results of a performance evaluation of the hybrid benchmark over various database products is included for untyped and typed XML with and without clearing the database cache.