An important application of XML is the interchange of electronic data (EDI) between multiple data sources on the Web. As XML data proliferates on the Web, applications will need to integrate and aggregate data from multiple source and clean and transform data to facilitate exchange. Data extraction, conversion, transformation, and integration are all well-understood database problems, and their solutions rely on a query language. We present a query language for XML, called XML-QL, which we argue is suitable for performing the above tasks. XML-QL is a declarative, ``relational complete'' query language and is simple enough that it can be optimized. XML-QL can extract data from existing XML documents and construct new XML documents.
Keywords: XML, query languages, electronic-data interchange (EDI)
Introduction
The goal of XML is to provide many of SGML's benefits not available in HTML and to provide them in a language that is easier to learn and use than complete SGML. These benefits include user-defined tags, nested elements, and an optional validation of document structure with respect to a Document Type Descriptor (DTD).
The goal of XML is to provide many of SGML's benefits not available in HTML and to provide them in a language that is easier to learn and use than complete SGML. These benefits include user-defined tags, nested elements, and an optional validation of document structure with respect to a Document Type Descriptor (DTD).
One important application of XML is the interchange of electronic data (EDI) between two or more data sources on the Web. Electronic data is primarily intended for computer, not human, consumption. For example, search robots could integrate automatically information from related sources that publish their data in XML format, e.g., stock quotes from financial sites, sports scores from news sites; businesses could publish data about their products and services, and potential customers could compare and process this information automatically; and business partners could exchange internal operational data between their information systems on secure channels. New opportunities will arise for third parties to add value by integrating, transforming, cleaning, and aggregating XML data. In this paper, we focus on XML's application to EDI. Specifically, we take a database view, as opposed to document view, of XML. We consider an XML document to be a database and a DTD to be a database schema.