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The XML Revolution Technologies for the future Web Anders Møller & Michael I. Schwartzbach BRICS, University of Aarhus http://www.brics.dk/~amoeller/XML/ First published: March 2000 Latest revision: October 2003 This slide collection provides an introduction and overview of XML, Namespaces, XInclude, XML Base, XLink, XPointer, XPath, DTD, XML Schema, DSD, XSLT, XQuery, DOM, SAX, and JDOM including selected links to more information about each topic. About this tutorial... This slide collection about XML and related technologies is created by Anders Møller http://www.brics.dk/~amoeller and Michael I. Schwartzbach http://www.brics.dk/~mis at the BRICS research center at University of Aarhus, Denmark. Copyright © 2000-2003 Anders Møller & Michael I. Schwartzbach Reproduction of this slide collection is permitted on condition that it is distributed in whole, unmodified, and for free, and that the authors are notified. The slide collection is aimed at computer scientists, software engineers, and others who want to know what this XML thing is all about. It covers both the basic XML concepts and the related technologies for document linking, describing classes of documents, stylesheet transformation, and database-like querying, from a technical but high-level point of view. Based on the essential XML-related specifications, the slides are designed with concrete motivation and technical contents in focus, for the reader who wishes to understand and actually use these technologies. A PDF version suitable for printing and off-line browsing is available upon request. Feedback is appreciated! Please send comments and suggestions to amoeller@brics.dk. 2 See also our tutorial Interactive Web Services with Java covering Web programming with Java, JSP, Servlets, and JWIG. 3 Contents 1. HTML and XML - structuring information for the future (24 pp.) 2. Namespaces, XInclude, and XML Base - common extensions to the XML specification (9 pp.) 3. DTD, XML Schema, and DSD - defining language syntax with schemas (28 pp.) 4. XLink, XPointer, and XPath - linking and addressing (26 pp.) 5. XSL and XSLT - stylesheets and document transformation (21 pp.) 6. XQuery - document querying (19 pp.) 7. DOM, SAX, and JDOM - programming for XML (17 pp.) 8. W3C - some background on the World Wide Web Consortium (5 pp.) See also the tutorial Interactive Web Services with Java covering Web programming with Java, JSP, Servlets, JWIG, SOAP, WSDL, and UDDI. 4 Markup Languages: HTML and XML HTML - original motivation, development, and inherent limitations: l Hyper-Text Markup Language - the Web today l Original motivation for HTML - some history l Compact and human readable - alternative document formats l From logical to physical structure - requirements from users l Stylesheets - separating logical structure and layout l A tiny stylesheet - a CSS example l Different versions of HTML - a decade of development l Different browsers - obtaining compatibility l Syntax and validation - HTML as a formal language l Browsers are forgiving - the real world l Structuring general information - not everything is hypertext l Problems with HTML - why HTML is not the solution XML as the universal format for structuring information: l What is XML? - the universal data format l HTML vs. XML - the key differences l A conceptual view of XML - XML documents as labeled trees l A concrete view of XML - XML documents as text with markup l Applications of XML - an XML language for every domain l The recipe example - designing a small XML language l From SGML to SML - a word on doc-heads and development l SGML relics - things to avoid l XML technologies - generic languages and tools for free l XML activity - development and applications Selected links: l Basic XML tools 5 l Links to more information 6 Hyper-Text Markup Language HTML: Hyper-Text Markup Language What is hyper-text? l a document that contains links to other documents (and text, sound, images...) l links may be actuated automatically or on request l linked documents may replace, be inlined, or create a new window l most combinations are supported by HTML What is a markup language? l a notation for writing text with markup tags l the tags indicate the structure of the text l tags have names and attributes l tags may enclose a part of the text The start of the HTML for this page, with text, tags, and attributes:

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Hyper-Text Markup Language

What is hyper-text?

• a document that contains links to other documents (and text, sound, images...)
• links may be actuated automatically or on request
• linked documents may replace, be inlined, or create a new window
• most combinations are supported by HTML

8 Original motivation for HTML Exchange data on the Internet: l documents are published by servers l documents are presented by clients (browsers) HTML was created by Tim Berners-Lee and Robert Caillau at CERN in 1991: l the motivation was to keep track of experimental data HTML describes only the logical structure of documents: l browsers are free to interpret markup tags as they please l the document even makes sense if the tags are ignored HTML combined well-known ideas: l hyper-text was known since 1945 l markup languages date back to 1970 9 Compact and human readable Many document formats are very bulky: l the author controls the precise layout l all details, including many font tables, must be stored with the contents In comparison, HTML is slim: l the author sacrifices control for compactness l only the actual contents and its logical structure is represented Sizes of documents containing just the text "Hello World!": PostScript hello.ps 11,274 bytes PDF hello.pdf 4,915 bytes MS Word hello.doc 19,456 bytes HTML hello.html 44 bytes Compactness is good for: l saving space on your server l lowering network traffic (Don't worry about voluminous markup - specialized compression techniques are emerging.) Furthermore, HTML documents can be written and modified with any rawtext editor.

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