Everything You Always Wanted To Know About XML But Were Afraid To Ask

“ Everything you always wanted to know about XML * * But were afraid to ask”

XML basics

A bit of web history

XML in detail

Where is XML used?

Creating XML

Manipulating XML

Pros and cons

XML basics

<?xml version=" 1.0 "?>

<manual id=" CRDA/ULCC/IMP/BPM/1.0 ">

<title> Biscuit Procedures Manual </title>

<author> Ruth Vyse </author>

<date> 1998-04-01 </date>

<content>

<heading> Purpose </heading>

<para> This document describes the procedures for

<list>

<item> provision of an adequate quantity of biscuits </item>

<item> provision of an adequate variety of biscuits </item>

</list>

</para>

</content>

</manual>

XML declaration

Elements

Attributes

Well-formed

Valid?

A bit of web history

SGML

HTML

Cascading Style Sheets (CSS)

Javascript

Standard Generalized Markup Language (SGML)

ISO Standard 8879:1986

Define structured document types

Markup languages for structured documents

Main components -

Elements delimited by tags

Attributes

Character data

Entities

Hypertext Markup Language (HTML)

An application of SGML

Hyperlinks / hypertext

Designed for structural markup of documents

Evolution:

4 major versions

Non-standard extensions (Netscape, MS)

Superseded by XHTML

Cascading Style Sheets (CSS)

body { font-family: serif ;

text-align: justify ;

margin: 0pt ;

background-color: white ;

color: black }

h1, h2, h3 { font-family: sans-serif ;

font-weight: bold ;

text-align: left ; }

.reverse { background-color: black ;

color: white }

Non SGML syntax

Properties cascade to descendants

Styles can be defined:

In external files

In document header

Inline

Javascript

Interface to browser functions

"Document object"

Event-driven interaction with

Forms

Images

Formatting

Security: limited IO

Object-oriented

ECMA 262 / ISO 16262

<html>

<head>

<script language=“ Javascript ”>

function helloWorld() {

var message = “Hello World”;

document.form[0].elements[0].value

= message;

}

</script>

</head>

<body>

<form>

<input type=“ text ”>

<input type=“ button ”

onClick=“ helloWorld ();”>

</form>

</body>

</html>

<mylink style =" color: blue; text-decoration: underline " onClick=" location='http://ndad.ulcc.ac.uk/'; "> NDAD </mylink>

XML in a little more detail

<?xml version=" 1.0 "

encoding=" ISO-8859-1 " ?>

<!DOCTYPE ead SYSTEM " ead.dtd ">

<ead audience=" internal ">

<eadheader langencoding=" ISO 639-3 ">

<titleproper> Lord Chancellor's Department:

Judge Advocate General's Office Case Index System </titleproper>

<date> 2002-08-06 10:52:20 </date>

</eadheader>

<archdesc level=" series " >

<scopecontent id=" AIM-PURPOSE ">

<head> Aim and purpose </head>

<p> A court martial is a court convened to try armed forces personnel who have committed military or criminal offences. </p>

</scopecontent>

</archdesc>

</ead>

Character encoding

DTD

Namespaces

Character encoding

ASCII: ISO 646

7 bit

ISO 8859

8 bit

Top half interchangeable

Unicode: ISO 10646

Code for every symbol of every language

Variable 8 - 32 bit encoding (UTF-8)

ASCII transparent in 8 bit encoding

Document Type Definition (DTD)

SGML compatible

Non XML syntax *

Defines document structure

Elements

Attributes

Entities

* pointy brackets notwithstanding

<!ELEMENT table (title, datafile, field+) >

<!ELEMENT title ( #PCDATA ) >

<!ELEMENT datafile (bytes, numrecs, maxrecsize) >

<!ELEMENT field (name, description, ddtext?, note?, choices?) >

<!ATTLIST table reference CDATA #REQUIRED >

<!ATTLIST datafile type CDATA #REQUIRED

location CDATA #REQUIRED>

<!ATTLIST field type CDATA #REQUIRED>

<!ENTITY NDAD "http://ndad.ulcc.ac.uk/" >

Namespaces

Mix and match XML applications

Avoid conflicting elements

Limited DTD compatibility

<?xml version=" 1.0 " encoding=" ISO-8859_1 " ?> <table reference = " CRDA/8/DS/1/1/1 "> <title> Court Details </title> <datafile type=" CSV " location ="/data/ready/8/court.txt "> <bytes> 20583 </bytes> <numrecs> 388 </numrecs> <maxrecsize> 65 </maxrecsize> </datafile> <description xmlns:html =" http://www.w3.org/1999/xhtml "> < html:p > For further details see the < html:a href=" /datasets/8/series.htm "> Series Catalogue < /html:a > . < /html:p > </description> </table>

Where is XML used?

Web

Desktop applications

New markup applications

Standards for data exchange

Configuration files

Web

Server side

on-the-fly transformation to HTML / XHTML using XSLT

Client side

rendered native using CSS

transformed to HTML / XHTML using XSLT

Metadata

Desktop applications

OpenOffice/StarOffice

Mozilla/Netscape 6+

MS Office 2000

Other applications

Encoded Archival Description (EAD)

Text Encoding Initiative (TEI)

Scalable Vector Graphics (SVG)

XHTML

Custom applications

Creating XML

By hand

XML editors

Programming

Using XML ...

XML editors

Non-validating

XML Notepad

Validating

Xmetal

XML Spy

XML Writer

Programming

A simple Perl example:

#!/usr/bin/perl

use XML::LibXML;

$parser = new XML::LibXML;

$doc = $parser ->parse_file(" myfile.xml ");

$root = $doc ->getDocumentElement;

@fields = $root ->getElementsByTagName(" field ");

foreach ( @fields ) { # do something # }

Manipulating XML

Document Object Model (DOM)

XPath

XML Stylesheets (XSL)

More XML applications

Document Object Model (DOM)

W3C recommendation

Application independent

Language/OS neutral

Hierarchical

Parent

Children

Siblings

Node types

Document

Element

Attribute

Text

Comment

Entity

+ 6 more

XPath

W3C recommendation

XML document as a tree of Nodes

Non XML syntax

Location paths

Relative: ../../tr

Absolute: /html/body/h1

Attributes: img@src

Axes: parent, child, sibling, etc

Functions

String: contains(), substring()

Array/node: last(), count(), position()

XML Stylesheets (XSL)

W3C Recommendation

XML syntax

Transformations (XSLT)

Formatting objects (XSL-FO)

XSLT processor e.g. Sablotron (sabcmd)

More XML applications

XHTML (strict, transitional)

XML-Schema

RELAX-NG

XLink

XPointer

XML Query

Open standard

Flexible

Transformable

Not going to be around forever

Simple

Complex

Machine-readable

Human-readable

</everything>

Everything You Always Wanted To Know About XML But Were Afraid To Ask

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