XML for Dummies

(and managers) Mark Pascall Technical Architect

Overview

What is XML?

Extensible Markup Language Many pieces in the XML puzzle Very fast moving First – back to basics….

Xlink HTM L XPointer XSLT XML XQuery SOA P XML Schem a Name space

How the Internet works….

Web Clients (Browser) Get me that text file OK here it is Web Server

Hypertext Mark-up Language

Here is the title

This is a piece of Text

A formatting language Browser knows how to interpret the tags.

What is Extensible Markup Language?

NOT a markup language Meta-markup Language Set of very simple rules XML provides a uniform method for describing and exchanging structured data Describes structure and semantics, not formatting

Meta Language 1. Use letters of alphabet.

2. Spaces between words.

3. Read from left to write.

…..

French English German …..

XML Specification 1. Tags must not overlap 2. Tags case-sensitive 3. Must have root tag …… SVG WML MathML …..

The XML Rules….

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2.

3.

4.

5.

6.

Single, unique root element Matching open/close tags Consistent capitalisation Correctly nested elements (no overlapping elements) Attribute values enclosed in quotes No repeating attributes in an element 3Months.com Web Development

Wakefield st Wellington New Zealand

Well Formed

History of XML

Standard Generalised Markup Language Been around since early 90’s XML is a sub-set of SGML (SGML-lite) XML has smaller and simpler syntax SGML’s development provides the foundation for XML XML is therefore not “bleeding edge”

Why XML is so powerful

Provides international, vendor independent standard for describing information Any information – structured or unstructured XML HTTP TCP/IP

XML Markup languages/vocabularies

Remember XML is a meta-language Anybody can create their own language Why would you want to?

Each language designed for a specific purpose….

Mathematical Markup Language (MathML)

x2 + 4x + 4 =0 x 2 4 x 4

Synchronized Multimedia Integration Language (SMIL)

Vector Markup Language

Wireless Markup Language

This is the first card.

This is the second card.

Hypertext Markup Language (HTML)

The Title

This is a piece of HTML

Or is it??

Next version of HTML = XHTML

XML Schemas and DTDs

XML is about communication Need to speak the same language Schemas/DTDs describe the vocabulary of the language i.e. what tags are used and how they can be organised Schemas will replace DTDs

An Example Schema

20/7/01 Bla Bla Bla

Introducing XSL-T

Extensible Stylesheet Language Standard ratified this year by W3C Way of transforming an XML document into another document

XML document

Transformation

XSLT document XSLT Processor Text HTML XML

Summary

The XML Specification = Meta-language for describing XML Mark-up languages XML Schemas (and DTD’s) describe the structure of a particular XML Mark-up language XSL-T documents transform XML document into another format (HTML, XML etc)

XML in Action – a case study

Agenda

Case study background Choosing a DTD/Schema Creating XML – the options Storing XML – the options Presenting XML – the options Solution Benefits Demo

Case study background

October 2001 – won contract to redevelop E-government website ( www.e-government.govt.nz

) Business requirements – Usual stuff (accessible, usable etc) – Guidelines compliant (squeaky clean)

“Content must be made available in a standard HTML format. Where information is provided in a proprietary format an alternative HTML version must also be made available.” Can’t just put it up as a PDF anymore

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Simple publishing process Future-proofed Constraints

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Limited budget

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Tight timeframe

Traditional options

Static site – Did not give simple publishing process for “unskilled” people Content Management System – Store information in RDBMS – Not good for “document centric” applications – Cost, timeframe, simple workflow requirements

The challenge – To create a system that allows non-technical authors to publish to guidelines compliant HTML (and eventually other formats) The solution – XML

Choosing a DTD/Schema

Make up your own Don’t reinvent the wheel!

Xml.org

We selected a subset of DocBook – Could handle all the information we needed to store – Supported by a growing number of products NZETC uses TEI

Creating XML – the Options

Use an XML editor – E.g. XML Spy, Xmetal, Framemaker etc – Allow you to create a document that conforms to a specified DTD/Schema – Problem: everybody potentially an author Convert Word documents to XML – Styles

Word (using Styles) Word is authoritative source DocBook XML XSL-T for convertion HTML (Internet) eBook Anything you want!!

Xcon Demo

Storing XML – the Options

Relational database Native XML Repository – E.g. Excelon, Tamino, Ipedo, Xindice – First generation products – At the time too immature/expensive On the file system

Presenting XML – the Options

Publishing to humans Need to “transform” XML to a format appropriate for humans Physical print – out of scope HTML obvious choice XSL-T to transform XML to HTML Not the only way to present to humans – SMIL, SVG, MathML etc – Audience must have software What about publishing “Raw” XML?

Organisation A Website XML document HTML document Organisation B Website HTML document Organisation C Website XML document

Demo