Xml Overview

XML OVERVIEW

Mohammad Elsheikh Salim Elsheikh ElgarraiLecturer - Shendi University (Sudan)

[email protected]

Topics in covered in this presentation

What is XML? History. Why XML?

The Data Problem. Weaknesses of HTML.

Key Features of XML. Extensibility Media and Presentation independence

Separation of contents from presentation Structure Validation

What is XML? Definition: The Extensible Markup Language (XML) is

a subset of SGML (Standard Generalized Markup Language). Its goal is to enable generic SGML to be served, received, and processed on the Web in the way that is now possible with HTML. XML has been designed for ease of implementation and for interoperability with both SGML and HTML.

Versions: XML 1.0, XML 1.1, XML 2.0

Historys The versatility for dynamic information

display was understood by early digital media publishers in the late 1980s prior to the rise of the Internet. In the mid-1990s some practitioners of SGML had gained experience with the then-new World Wide Web, and believed that SGML offered solutions to some of the problems the Web was likely to face as it grew. SGML added to the list of W3C's activities when he in 1995; work began in mid-1996.

History (Cont.) XML was compiled by a working group of eleven

members, supported by an (approximately) 150-member Interest Group. Technical debate took place on the Interest Group mailing list and issues were resolved by consensus or, when that failed, majority vote of the Working Group.

The name "XML“ has been selected. Other names that had been put forward for consideration included "MAGMA" (Minimal Architecture for Generalized Markup Applications), "SLIM" (Structured Language for Internet Markup) and "MGML" (Minimal Generalized Markup Language).

History (Cont.) The XML Working Group never met face-

to-face. The major design decisions were reached in twenty weeks of intense work between July and November 1996, when the first Working Draft of an XML specification was published. Further design work continued through 1997, and XML 1.0 became a W3C Recommendation on February 10, 1998.

The Data Problem How do I represent my “application”

data?

Performance (speed/time) Mutability Composition Security (encryption/identity)

Data Problem (Cont.) Open Information Management:

Interpretation Presentation Interoperation Portability Interrogation

Weaknesses of HTML Fixed set of tags

Not user extensible Dependency to “markup language” definition

process Dependency to vendors

Vendor proprietary tags Implementation not in sync

Netscape browser vs. IE Predefined semantics for each tag Predefined data structure

Weaknesses of HTML (Cont.)

No formal validation Does not support semantic search Based on solely on appearance

(rendering) NOT on content Formatting too simple

Limited control Won’t do complex documents Poor support for print and other media

Key Features of XML Extensibility Media and Presentation independence

Separation of contents from presentation Structure Validation

Extensibility You define your own markup languages (tags)

for your own problem domain Infinite number of tags can be defined

Need for domain-specific standards Tags can be more than formatting Tags can be anything

Data relationship Formatting Anything you want

Many domain-specific markup languages Portable data within domain-specific industry Portable across the various domain

Media (Presentation)Independence

Clear separation between contents and presentation

Contents of data What the data is Is represented by XML document

Presentation of data What the data looks like Can be specified by stylesheet (like css)

Media (Presentation)Independence (Cont.)

Same data can be presented to different communication medium HTML browser Voice device

Same data can be presented to different format Cell phone as WML Desktop as HTML

Separation of Contents fromPresentation

Searching and retrieving data is easy and efficient Tags give search’able information

Many applications use the same data in different ways Employee data can be used by

Payroll application Facilities application Human resource application

Enables portability of data Portable over time and space

Structure: HTML vs. XMLHTML (Automatic Presentation of Data)<b> ali mohammad 1234 </b> // Display in bold

XML (Automatic Interpretation of Data)<Employee>

<Name><firstName> ali</firstName><lastName> mohammad</lastName>

</Name><EmployeeID> 1234 </EmployeeID>

</Employee>

Structure Relationship

Employee is made of Name and employ-ID Name is made of firstName and LastName

Hierarchical (Tree-form) Faster to access Easier to rearrange Can be any number of depth

Enables to build large and complex data Portability of relationship and hierarchical

structure

Validation In addition to being well-formed, an XML document

may be valid. This means that it contains a reference to a Document Type Definition (DTD).

XML data is “constrained” by a Rule (or Syntax) Employee data has to have Name and Employee ID elements

Name has to have both firstName and LastName elements

<Employee><Name><firstName> ali</firstName><lastName> mohammad</lastName></Name><EmployeeID> 1234 </EmployeeID>

</Employee>

XML Document An XML document must start with an XML

declaration. It can include comments, XML processing

instructions, etc. It also has (exactly) one XML node (the

root node), which can have other nodes as children.

Note: XML is case-sensitive (unlike HTML)

XML Document<?xml version="1.0" encoding="ISO-8859-1"?><!-- Edited with XML Spy v4.2 --><!DOCTYPE Employees_list SYSTEM "example.dtd"> < Employees>

<Employee><Name><firstName> ali</firstName><lastName> mohammad</lastName></Name><EmployeeID> 1234 </EmployeeID></Employee><Employee><Name><firstName> ahmad</firstName><lastName> hassen</lastName></Name><EmployeeID> 2345 </EmployeeID></Employee>

</ Employees >

XML Document XML declaration – specifies the version

and character encoding (e.g., UTF-8 or ISO-8859-1)

Processing instructions – provide arbitrary “extra” information about the document (e.g., printing options)

Comments – who uses those, anyway?

XML Document Tags – enclosed between < ... > Elements – include everything from the

start tag to the end tag Attributes – key=”value” pairs specified

in the start tag of an element Text nodes – special type of node that

contains (part of) text inside an element An XML document is really just a tree

Thank you for your patience