XML is a flexible data format that has rapidly become the lingua franca of data exchange between inter-enterprise applications on the Internet. Hundreds of industry-specific XML dialects already exist. Bioinformatics data, financial products, legal documents, medical transcripts, and electronic-commerce transactions are some examples of the diverse kinds of data that are exchanged in XML. For the past four years, I have been a member of the World-Wide Web Consortium's XML Query Language working group, whose charter is to define XQuery, a standard query language for XML. In this talk, I will identify the characteristics of XML and the requirements of data-exchange applications that demand a new query language. I will describe how XQuery, a functional, strongly-typed query language, satisfies (most of) those requirements. A cast of thousands contribute to XQuery. I work most closely with Jérôme Siméon (IBM Watson Research). Together, we have built Galax (http://www.galaxquery.org), a complete implementation of XQuery 1.0, which I will demonstrate during the talk.