Well, what is the purpose of markup languages? Isn't the sole purpose of markup is to be able to process the marked-up content with a computer? Why would you ad

Well, what is the purpose of markup languages? Isn't the sole purpose of markup is to be able to process the marked-up content with a computer? Why would you add markup to your favorite verse if it wasn't to somehow feed it to machine for some purpose (analyze, typeset, etc.)? So when we have text with markup the text part is meant to be there for humans and the markup part is solely for computers. Now let's remove all text; now there's no content for humans at all, only for computers. How is this different from general-purpose data serialization? (Some of the samples you give, like SVG, may not have any text content at all; it's basically a drawing language.) Given that XML ecosystem has quite a few tools (e.g. several type description languages or a declarative data transformation language just to name a few) it's a very good general-purpose data serialization format.