It all started with cavemen and their cave drawings. All cave drawings were WYSIWYM (What You See is What You Mean). I mean (no pun intended), if you saw a cave drawing, in which a hunter was chasing a mammoth, it meant that a hunter was chasing a mammoth. There were no two ways to interpret the cave drawings. Then came alphabets and words. With words came plain text or documents. Then came XML/SGML for adding information to a document relating to its structure and/or content. An XML document contains both content (words) and an indication of what role the content plays.