XML surpasses HTML in that it allows data to be separate from the user interface, and can be processed by diverse platforms. HTML describes how to “display” the “data” in a browser, while XML is used to define the content, using tags only to describe the data. XML provides a tree-structured data format that is easy to deploy and can be broadly implemented.

HTML undermines internet interchange because it's small, fixed set of tags indicates only the appearance of an element of a document. HTML provides nothing to denote the data within a document, which cripples attempts to achieve reuse.

Automation with any forms-based application cannot be achieved with HTML. HTML lacks expressiveness, since it is limited to a fixed set of presentation-oriented tags, and lacks consistency, since there is no way to impose a rigorous data structure on top of those tags.