RE: When you create a markup language, what do your parent elementsmean?

["Costello, Roger L." <costello@mitre.org>]

Hi Folks,

These two markup languages have a consistent definition of what parent elements and child elements mean:

1. RDF
2. GML

Both languages specify that parent elements represent a resource or object and child elements represent properties or attributes.

Are those the only markup languages that have a consistent definition of what parent elements and child elements mean?

If one is creating a markup language and wants to adopt a consistent definition for parent elements and child elements, is resource/object and property/attribute the only way to accomplish it? 

Is an Object-Oriented approach to markup the only viable approach when one wants to have a consistent definition for parent elements and child elements? That would be quite astonishing, given that people such as Tim Bray argue that "XML is 180 degrees apart from OO".

/Roger