XML A brief introduction ---by Yongzhu Li. XML --- a brief introduction 2 CSI668 Topics in System Architecture SUNY Albany Computer Science Department

XMLXMLA brief introductionA brief introduction

---by Yongzhu Li

XML

--- a brief introduction 2CSI668Topics in System Architecture

SUNY Albany Computer Science Department

XMLeXtensible Markup Language

designed to describe data.

a family of technologies

platform-independent

free and extensible

XML



Basic Concepta markup language is a mechanism to identify structures in a document.

the XML specification defines a standard way to add markup to documents.

a meta-language for describing markup languages

provides a facility to define tags and the structural relationships between them

XML



BackgroundSGML Standard Generalized Markup Language (ISO

8879) provides arbitrary structure, but too difficult to

implement just for a web browser.

HTML A subset of SGML with a fixed tag semantics

and set, lack of flexibility and extensibility Lack of extensibility

XML



Background IIXML simplified SGML, extensible looks like HTML but isn't HTML any fully conformant SGML system will

be able to process XML documents but, XML documents does not require a

system that is capable of the full conformance of SGML

XML



Evolving HistoryW3 Consortium began work in Aug. 1996

XML 1.0 Released by W3C on Jan. 10, 1998

XML 2.0 Introduced on Oct. 6, 2000

XML 3.0 Under drafting and evaluating

XML



What XML looks likeprolog --- XML file declaration <?xml version=“1.0”?>

comment 

processing instruction, PI <?xml-stylesheet type="text/css"

href="first.css"?>

element and its attribute <price currency ="$">15.50</price>

XML



First Sample

single XML file only provide structured data

No formatting information

browser don’t know how to display

a single XML document

XML



CSSCascading Style Sheets

also work well with HTML

delaring CSS within XML file <?xml-stylesheet type="text/css"

href="first.css"?>

separate data content with its form

only provide formatting information, lack of manipulation on data

XML



First Sample IIFormated Source CSS file

XML



Interesting CSSCascading layers z-index position

sampleXMLCSS

XML



Interesting CSS IIFilter filter:glow(color=blue, Strength=5);

sampleXMLCSS

XML



XSLeXtensible Stylesheet Languagedeclaring XSL within XML

<?xml-stylesheet type="text/xsl" href="first.xsl"?>

transform XML to HTML filedefining and formating XML parts and patternsfar more sophisticated but powerful than CSS

XML



XSL by SampleData Sorting XSL Source

Data Filter XSL Source

XML



Namespace

a collection of element type and attribute names

distinguish between duplicate element type and attribute names

XML



Namespace Samples<books xmlns:book=“books.dtd” xmlns:journal =“journal.dtd”> <book:title>

….. </book:title> <journal:title>

….. </journal:title>

XML



Name Space Sample II<html xmlns:html=“http://www.w3.org/TR/REC-html40”>

<html:h1>some message</html:h1>

<html:a href= mailto:[email protected]> email me</html:a>

XML



DTDDocuments Type Definitiona model for describing the structure of information. Well formed XML and Valid XMLA valid XML must follow a specific DTD

XML



Why DTDIndependent organizations use a common DTD for interchanging data. applications use DTD to verify the data received from the outside world is valid.

XML



DTD IIDeclaring DTD within XML <!DOCTYPE books SYSTEM “book.dtd”>

Element Declaration within DTD <!Element title (#PCDATA)> <!Element book (title,author+, press,

price)> <!Element books (book*)>

Attribute Declaration <!ATTLIST price currency ($|€|¥)’$’>

Eric:

Parsable Character Data

Eric:

Parsable Character Data

XML



DTD Weaknesswritten in a different (non-XML) syntax.

don’t support namespace

only offer extremely limited data types.

have a complex and fragile extension mechanism

XML



Schemareplacement of DTDs for XML

more primitive data types

namespace support.

itself is a well formed XML and validated by Schema DTDs

XML



XML Application Domain

Electronic Data Interchange

search engine

web application

distributed documentation and computing

XML



Some other XML applications

WML, Wireless Markup Language

CML, Chemistry Markup Language and MathML

OSD, Open Software Description

OFX, Open Financial Exchange

XML



XML Application Structure

Viewer #1

e.g. Retail Agent Viewer #2

e.g. Customer

XML Processor

Application Server

DB 1 DB 2 DB .. DB nMay be heterogeneous DBs

Other process

CSS/ XSL translation

CSS/ XSL translation

XML



DOMDocument Object Model

program interface for XML

represents a tree view of the XML

documentElement as a root

childNode for other branch

each node is an object Node Interface Model

XML



SAXthe Simple API for XMLanother programming interface for XMLevent-based APIuse call-back functions to handle parsing eventSAX and DOM are two major APIs for XML application development.

XML



SVGScalable Vector Graphic

XML application

describe two-dimensional vector graphic shapes, images and text

reduced the network traffic

reduced server overload

VML by Microsoft and PGML by Adobe

XML



XHTMLeXtensible HTML

HTML defined by XML

well-formed HTML

tag names must be in lowercase

XML



Things under going…Xlink and Xpointer allows elements to be inserted into XML in order to

create and describe links between resources provide multi-directional hypertext and hypermedia

support proposal recommendation on Dec. 20, 2000

XML Protocol to develop technologies which allow two or more

peers to communicate in a distributed environment, using XML as its encapsulation language.

requirement draft on Dec. 19, 2000

Thank YouThank You

谢谢谢谢