XML Basics Chao-Hsien Chu, Ph.D. School of Information Sciences and Technology The Pennsylvania State University Extensible Meta Language Markup Language

Information Information Age Processing Representation Storage Retrieval SearchSharing Management Interchange

IS there such a creation ? The Needs for Information Interchange  Power  Flexibility  Simplicity  Fault tolerance  Scalability  Interoperability  Open standard  Extensible  Character-based  Human-readable

IS There Such a Creation?  Power  Flexibility  Simplicity  Fault tolerance  Scalability  Interoperability  Open standard  Extensible  Character-based  Human-readable HTML SGML XML XXX ?XXX ??? X XXXX Criteria

Weaknesses of HTML  HTML isn’t extensible – can’t define custom tags.  HTML is display-centric.  HTML isn’t usually directly reusable  HTML only provide one view of data.  HTML has little or no semantic structure.  Getting bigger and slower!  Not fault tolerance. XML will complement, rather than replace, HTML

The Buzz Words Around XML  SVG – Scalable Vector Graphics Language  OFX – Open Financial Exchange  SGML – Standard Generalized Markup Language  DTD – Document Type Definition  DSSSL – Document Style Semantics and Specification Language  CSS – Cascading Style Sheet  XSL – XML Stylesheet Language  DOM – Document Object Model....

Basics of XML XML What? Why? Who? Where? When? How?

What is XML?  XML stands for Extensible Markup Language.  Markup is the code, embedded with the document, which store the information required for electronic processing.  XML is extensible because it predefines no tag but lets the user create tags that are needed for application.  XML is a meta language because it can be used to define markup languages.

Family of Markup Languages  GML – Generalized Markup Language  SGML – Standard Generalized Markup Language  HTML – Hyper Text Markup Language  XML – Extensible Markup Language  XHTML – Extensible Hyper-Text Markup Language  CML - Chemistry Markup Language  MathML – Mathematical Markup Language  SVG – Scalable Vector Graphic  SMIL – Synchronized Multimedia Integration Language  HDML – Handheld Device Markup Language  WML – Wireless Markup Language  OEB – Open eBook Structure Specification

Genealogy of Markup Languages GML (1969) SGML (1985) XML (1998) HTML (1993) XHTMLSVGSMILHDMLOEB IBM ISO 8879 W3C CERN

SGML XML Genealogy of Markup Languages HTML XSL

Advantages of XML  Common language for system-to-system communication  Enables loose connectivity, yet tight integration  Relatively easy to implement conversion from an RDB record to an XML message.  Platform independent  Scalable  XML Signature provides message and party authentication.

Traditional vs. Nontraditional Document Information Structure Format Traditional Format InformationStructure Nontraditional

Ways of Displaying XML Format Information (Document) Structure (DTD) XSL DHTML + CSS DSSSL CGI + Script

Write One Publish Many Idea XML Document Print out CD ROM Web WAP, etc. Process

XML for Information Interchange CAD Package Word Processor Statistical Processing Spreadsheet Package XML

Demand for Platform Independent Technology InternetXHTML XMLJava Platform DataProcessing Presentation

Selected XML Applications Middle-Tier Servers:  Personalized Frequent-Flyer Website  Building an Online Auction Website  Anatomy of an Information Server E-Commerce:  Electronic Data Interchange (EDI)  Collaboration in an e-commerce Supply Web

Selected XML Applications Portals:  Enterprise Information Portals (EIP) Syndication:  Information and Content Exchange (ICE) Publishing:  PC World Online Content Management:  Enterprise Data Management

Selected XML Applications Content Acquisition:  Integrating Legacy Data Schema:  Building a Schema for a Product Catalog Stylesheet:  A Stylesheet-Driven Tutorial Generator. Navigation – Application Integration:  Application Integration Using Topic Map

Components of XML Systems XML Parser (Processor) XML Application XML Document (Contents) XML DTD (Rule) Well-Formed (Syntax) Validate (Structure)

Well Formed Document Here are some general guidelines:  At least one root element.  All elements must contain both start and end tags.  Tags are case sensitive  No overlapping tags. Elements must nest inside each other properly.  Attribute values must be enclosed in quotes.  An empty element must end with “/>”  The text characters ( ) and (“) must always be represented by character entities. Well formed XML documents are those documents that are syntactically correct.

(optional) How a Parser Interprets XML - Validate XML Document Data Type Definition Issue Warning/Stop Processing Further Processing Well Formed? DTD? Valid? Issue Warning/Stop Processing no yes

Popular Parsers for XML  MSXML – Microsoft’s IE  Gecko – Netscape  IBM XML Parser for Java (  Data Channel XJ Parser ( )  SUN XML Parser for Java ( )

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