The Niagara Internet Query System.

TLDR

Future Internet visions involve vast Web‑accessible XML files, yet existing XML query engines alone cannot support Internet‑scale querying. The Niagara Internet Query System aims to locate relevant XML files and manage unpredictable or infinite data sources. It combines the Niagara XML‑QL processor with a text‑in‑context search engine, implements a get‑partial operation on blocking operators, inserts synchronization packets to ensure consistency, and is available as public‑domain software at http://www-db.cs.wisc.edu/niagara/. Category: Research.

Abstract

Many projections envision a future in which the Internet is populated with a vast number of Web-accessible XML files—a “World-Wide Database”. Recently, there has been a great deal of research into XML query languages to enable the execution of database-style queries over these XML files. However, merely being an XML query-processing engine does not render a system suitable for querying the Internet. A truly useful system must provide mechanisms to (a) find the XML files that are relevant to a given query, and (b) deal with remote data sources that either provide unpredictable data access and transfer rates, or are infinite streams, or both. The Niagara Internet Query System was designed from the bottom-up to provide these mechanisms. It finds relevant XML documents by using a novel collaboration between the Niagara XML-QL query processor and the Niagara “text-in-context” XML search engine. To handle infinite streams and data sources with unpredictable rates, it supports a “get partial” operation on blocking operators in order to produce partial query results, and inserts synchronization packets at critical points in the operator tree to guarantee the consistency of (partial) results. The Niagara Internet Query System is public domain software that can be found at http://www-db.cs.wisc.edu/niagara/. Category: Research.