XML Extensible Markup Language

XML2 Weaknesses of HTML n Displaying very long pages –Only top-level structuring is and –Only top-level structuring is and –No contextual headings n Can mistakenly use an instead of an n Can mistakenly use an instead of an

XML3 Weaknesses of HTML n Control over page layout –Ad-hoc fixes n Tables with no borders n One-pixel images

XML4 Weaknesses of HTML n Hyperlink types –Only a single type of hyperlink –Want multiple types n See also pages n Part of pages

XML5 Weaknesses of HTML n Delivery of multiple types of information –Conversion to HTML loses inherent structure

XML6 History n Until 1996, the SGML community hadn't taken an active interest in the web n Mid-1996 –80 SGML experts joined with W3C to form an SGML working group –Wanted to develop a markup language with power and generality of SGML and easily implementable on the web

XML7 History n Mid-1996 –This language had to n Support generalized markup on the web n Produce valid SGML-like documents n Provide hyperlinking capabilities compatible with the URL approach n Provide a generic, powerful style-sheet capability

XML8 History n July 1997 –W3C XML Special Interest Group

XML9 What It Is n Subset of SGML –Less complex –Easier to use n Can invent your own tagsets n Can make documents self-describing n Can validate your documents n Can break-up large documents into manageable chunks