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) 1. 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...