Iyer N. Subramanian

A declarative language for querying and restructuring the Web

World Wide Web is a hypertext based, distributed information system that provides access to vast amounts of information in the Internet. A fundamental problem with the Web is the difficulty of retrieving specific information of interest to the user, from the enormous number of resources that are available. We develop a simple logic called WebLog that is capable of retrieving information from HTML (Hypertext Markup Language) documents in the Web. WebLog is inspired by SchemaLog, a logic for multidatabase interoperability. We demonstrate the suitability of WebLog for: querying and restructuring Web information; exploiting partial knowledge users might have on the information being queried; and dealing with the dynamic nature of information in the Web. We illustrate the simplicity and power of WebLog using a variety of applications involving real life information in the Web.

On the logical foundations of schema integration and evolution in heterogeneous database systems

Developing a declarative approach to schema integration in the context of heterogeneous database systems is a major goal of this research. We take a first step toward this goal in this paper, by developing a simple logic called SchemaLog which is syntactically higher-order but has a first-order semantics. SchemaLog can provide for a logical integration of multiple relational databases in a federation of database systems. We develop a fixpoint theory as well as a sound and complete proof theory for the definite clause fragment of SchemaLog and show their equivalence to the model-theoretic semantics. We argue that a uniform framework for schema integration as well as schema evolution is both desirable and possible. We illustrate the simplicity and power of SchemaLog with a variety of applications involving database programming (with schema browsing), schema integration, schema evolution, and cooperative query answering.

Tables as a paradigm for querying and restructuring (extended abstract)

Tables are one of the most natural representations of real-life data. Previous table-based data models (such as relational, nested relational, and complex objects models) capture only a limited variety of real-life tables. In this paper, we study the foundations of tabular representations of data. We propose the tabular database model for handling a broad class of natural data represent at ions and develop tabular algebra as a language for querying and restructuring tabular data. We show that the tabular algebra is complete for a very general class of transformations and show that several languages designed for very different purposes can naturally be embedded into the tabular model, We also demonstrate the applicability of our model as a theoretical foundation for on-line analytical processing (OLAP), an emerging technology for complementing the robust data management and transaction processing of DBMS with powerful tools for data analysis.

Languages for multi-database interoperability

Database system technology which there is a moliferation has reached a of inderrendent stage now in svstems storing and manipul~ting enormous amount of data. Unfortunately, these systems typically have their own data models, communication processing protocols, query processing systems, concurrency control protocols, consistency management, and other similar aspects of database systems. There is also an increasing need for In teroperability among these systems. Though considerable amount of research has been done in the area of database interoperability, most of it has resulted in solutions that are ad-hoc and procedural. We have developed a declarative environment in which multiple heterogeneous databases interoperate by sharing, interpreting, and manipulating information, in a uniform way. An important criterion for Interacting with multiple databases is the abiIity to query them in a manner independent of the discrepancies in their structure and data semantics. In this demo, we exhibk two languages for querying across multiple databaaes which store semantically similar data using heterogeneous schema, ss well as for restructuring the queried data: (1) SchemaLog – a language that has its foundations in logic and (2) SchemaSQL – a language based on a principled extension to SQL.

On implementing SchemaLog —a database programming language

Efficient implementation of advanced database programming languages call for investigating novel architectures and algorithms. In this paper, we discuss our implementation of SchemaLo& a logic-based database programming language, capable of offering a powerful platform for a variety of database applications involving data/meta-data querying and restructuring. Our architecture for the implementation is based on compiling SchemaLog constructs into an extended version of relational algebra called SchemaLog. Based on this algebra, we develop a top-down algorithm for evaluating SchemaLog programs. We discuss three alternative storage stmctures for the implementation and study their effect on the efficiency of implementation. For each storage structure, we propose strategies for implementing our algebraic operators. We have implemented all these strategies on top of Microsoft Access DBMS running on Windows 3.1, and have run an extensive set of experiments for evaluating the efficiency of alternative strategies under a varied mix of querying and restructuring operations. We discuss the results of our experiments and conclude with a discussion of a graphic user interface for SchemaLog program development, that has also been implemented.