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Introduction to HTML/XHTML

Introduction to HTML/XHTML. Elena Pierazzo. GO HERE:. http :// www.cch.kcl.ac.uk/legacy/teaching/ma_foundation/HTML /. Markup languages. Markup before computers Computerised markup different languages (HTML, TACT …) different objectives variety of syntax

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Introduction to HTML/XHTML

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  1. Introduction to HTML/XHTML Elena Pierazzo

  2. GO HERE: http://www.cch.kcl.ac.uk/legacy/teaching/ma_foundation/HTML/

  3. Markup languages • Markup before computers • Computerised markup • different languages (HTML, TACT …) • different objectives • variety of syntax • but what is the general objective?

  4. BETTER EXAMPLE OF PRE-COMPUTERS MARKUP??

  5. SGML The markup language protagonist: SGML (Standard Generalised Markup Language) – ISO 8879:1986 and descendant: HTML and XML

  6. Elements • Main structure of the languages based on SGML • Contains anything that can be viewed as a structural component of a text • “Structure” can be: a paragraph, a section but also a word or a single character or even the space between two words

  7. Tags Elements are delimited by tags and enclose content <element>content</element> start-tag end-tag

  8. Attributes Elements can have attributes to specify some detail, or classify, or…. <element attribute=“value”>content</element>

  9. You can invent your own elements!! • Really! • But you have to declare them in a sort of a grammar called Document Type Definition or DTD • DTDs define: • Which elements you can use • Where you can use them • What content and attributes they can have • If the document respects the rules defined within the DTD, it is called valid

  10. Relationship In SGML based languages relations among elements are: • Hierarchical • Ordinal Relations among elements can be described as family relations (parents, ancestor, children, siblings…)

  11. Given 2 elements, A and B: • A follows B • B follows A • A contains B • B contains A

  12. Nesting of elements <b><i>Some text</i></b>

  13. Overlapping <b><i>Some text</b></i> but sometimes…

  14. HTML the origin • “Invented” in 1991 by Tim Berners-Lee, based on SGML • Wrote the HTML DTD and the first browser • Date of birth of the WWW • He, and anybody else, could not have imagined… • The WWW in the ’90: the Wild, Wild West of HTML • 75% of the code used to produce a browses is to fix bad HTML

  15. W3C • In 1994 the World Wide Web Consortium was funded by TBL • A sort of Guardian of the quality of the web: offer a validation service fro HTML, CSS and much more

  16. XML • Invented in 1996, based on SGML • Simplification of SGML, too complex, too rich, too flexible • XML Few rules, but non flexible • E.g. overlapping is NOT allowed, EVER • Case sensitive

  17. From HTML to XHTML • XHTML = an HTML written in XML (and not on SGML) • More rigorous and “clean” • Several flavours • Strict • Transitional • Frameset

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