World-Wide Markup Language
“The HyperText Markup Language is an SGML format.” [Tim Berners-Lee, 1991, “About HTML”]
Standard, Open Document Formats since the 1960s (GCA’s GenCode, IBM’s GML)
SGML [ISO 8879:1986] can prove the validity of any document using standardized DTDs, complex structuring, extensions
In 1990, Berners-Lee picked tags from a sample SGML DTD and added a “killer feature”: links
The World-Wide HTML tagset is limited to the 80/20 rule
XML allows Community-Wide Markup Languages,combining SGML’s power with HTML’s simplicity