Transcription: While SGML was extremely strict and had strict content type checking, HTML had very limited checking, almost next to none. So HTML was not a good language for representing data. It was a good language for representing text-based content, but when it came down to data, say coming from a database, it really fell short. Now SGML on the other hand provided strict content checking, but it also provided a number of other features that made it more complex. Well this is why XML exist today.
(.mp4)