λ-DB

• Published in: ACM SIGMOD Record
• Main Authors: Fegaras, Leonidas, Srinivasan, Chandrasekhar, Rajendran, Arvind, Maier, David
• Format: Article in Journal/Newspaper
• Language: English
• Published: Association for Computing Machinery (ACM) 2000
• Subjects: DML
• Online Access: http://dx.doi.org/10.1145/335191.335494; https://dl.acm.org/doi/pdf/10.1145/335191.335494

The λ-DB project at the University of Texas at Arlington aims at developing frameworks and prototype systems that address the new query optimization challenges for object-oriented and object-relational databases, such as query nesting, multiple collection types, methods, and arbitrary nesting of collections. We have already developed a theoretical framework for query optimization based on an effective calculus, called the monoid comprehension calculus [4]. The system reported here is a fully operational ODMG 2.0 [2] OODB management system, based on this framework. Our system can handle most ODL declarations and can process most OQL query forms. λ-DB is not ODMG compliant. Instead it supports its own C++ binding that provides a seamless integration between OQL and C++ with low impedance mismatch. It allows C++ variables to be used in queries and results of queries to be passed back to C++ programs. Programs expressed in our C++ binding are compiled by a preprocessor that performs query optimization at compile time, rather than run-time, as it is proposed by ODMG. In addition to compiled queries, λ-DB provides an interpreter that evaluates ad-hoc OQL queries at run-time. The λ-DB system architecture is shown in Figure 1. The λ-DB evaluation engine is written in SDL (the SHORE Data Language) of the SHORE object management system [1], developed at the University of Wisconsin. ODL schemas are translated into SDL schemas in a straightforward way and are stored in the system catalog. The λ-DB OQL compiler is a C++ preprocessor that accepts a language called λ-OQL, which is C++ code with embedded DML commands to perform transactions, queries, updates, etc. The preprocessor translates λ-OQL programs into C++ code that contains calls to the λ-DB evaluation engine. We also provide a visual query formulation interface, called VOODOO, and a translator from visual queries to OQL text, which can be sent to the λ-DB OQL interpreter for evaluation. Even though a lot of effort has been made to make the implementation of our ...