Beyond HTML: Extensible Markup Language (XML) Tim Cole Tom Habing Grainger Engineering Library Information Center University of Illinois at UC 2 June 2000

Text as Ordered Hierarchy of Content Objects E.g.: A book contains chapters, which contain paragraphs, which contain sentences,... This model (DOM) underlies SGML, HTML, & XML Content Objects can be Presentational (e.g., as in HTML) or Descriptive (e.g., as in SGML, XML) Allowed Object Names can be Finite (as in HTML) or Extensible (as in SGML, XML) –Thus SGML & XML are often described as “meta” markup languages

ML Basics - Markup & Content Markup (Tags) Content J. L. Pena J. L. Pena Attributes J. L. Pena Entities J. L. Peña J. L. Peña Others:

Markup Language Differences XML Stricter Than HTML or SGML –Must Close ALL Tags –Attributes MUST BE Enclosed in Quotes –All Mark-Up is CASE-SENSITIVE XML/SGML: no fixed tags, no predefined style XML/SGML Are Extensible –Fixed Elements (HTML) vs. Rules (XML, SGML) –XML Tags Can Describe the Content XML Simpler Than SGML, Optimized for Web

Well-formed XML vs. Valid XML If a Document Follows the Syntactic Rules for XML, it is WELL-FORMED. –Matching open and close tags –No overlapping content objects (regions) –Correct use of markup delimiters, entities, etc. Only Entities Allowed in Well-Formed are Unicode, > < " and & If it Also Adheres to the Content Models as Defined in a Document Type Definition, it is Also VALID.

Document Type Definition DTD Defines Allowable Content Models, Attributes, & Entities for a Class of XML Documents.

First Demonstration Create a Simple, Well-Formed XML Document, using MS Notepad –Book, Author, Title, ISBN, Link Open File in MS Internet Explorer Attach a CSS style sheet Re-Open in MS Internet Explorer

Typical XML File … document content...

Style Sheets: CSS & XSLT Cascading Style Sheets: –On-Screen Formatting & Presentation –Work with Both HTML & XML Extensible Style Sheet Language Transformations –Transforms Between XML DTDs or XML to HTML –Allows Re-Ordering of Content, Selective Display of Content, & Insertion of Generated Content –Extensions Allow Dynamic Modification of Content –Available as Application Programming Interface

XML Namespaces Allows Mixing of Multiple XML Schemas –XML Documents that Also Contain Fragments of HTML –Simultaneous Support of Multiple Metadata Schemas (e.g., Resource Description Framework, Dublin Core, UIUC DLI Metadata Schema) Rules for Namespaces & Other Schema Extension Models Still Under Development

Advanced Demo Add Doctype Declaration (for Valid XML) –Open DTD in XML Authority Open File in XML Notepad, XML Pro, XMetaL Attach an XSL Stylesheet Open in MS Internet Explorer –Server Side Implementation of an XSL Stylesheet MS SQL Server Data to XML Script to load XML into database

Examples from DLI Full-text Article Examples –A Large-Scale XML Testbed RDF / DC / IDLI Metadata –Interoperability Using XML Namespaces Browsing the ASM Metals Handbook in XML –Selective Display of Content Using XSLT ACES Agronomy Handbook in XML –Dynamic Table of Contents Using XML DOM

Future Directions XML and Databases XHTML -- Next Generation HTML Schemas -- Next Generation DTDs Xlink/XPointer -- Advanced Linking Xforms -- Advanced HTML Forms MathML -- Mathematics markup SVG -- Scalable Vector Graphics markup

Tools for Authoring XML Notepad XML Notepad XML Pro XML Authority XMetaL ArborText