What does it have over legacy EDI systems, or any other approach?

Because XML promises to improve the way companies exchange and present information over the Internet.

XML can benefit e-commerce by enabling back-end systems (databases) to communicate business transaction information.

For example, business partners can standardize on a specific XML syntax that describes a purchase order, or a parts ordering system supplied by a web database application, and automate the information's transfer across the Internet.

XML is ideal for building these systems because it allows formatting data for easy-to-process, platform-neutral exchange between business partners.