Come to think of it, perhaps the problem is more that we equate an "XML document" to a "web resource". What we perhaps need is a way of distributing a single XML document over a large collection of web resources, and then navigating around that XML document seamlessly, using XPath?Of course we can do that crudely already, using entities or XInclude. Perhaps we just need a smarter implementation of transclusion, where the document fragments are fetched on demand when XPath navigation needs them, rather than being assembled eagerly by the XML parser.