XML The Overview

Three Key Questions• What is XML?

• What Problems does it solve?

• Where and how is it used?

What XML IS• eXtensible • A set of rules for creating and implementing

markup languages that describe the structure of various kinds of documents and data

• Unicode text documents• A cross platform, long term data format

What XML Is Not• A programming language

• A network transport protocol (such as http or TCP/IP)

• A database

• A replacement of HTML

• The cure to all evils

What Problems Does it Solve• It provides a standardized method of communicating

data between systems, browsers and applications• Provides the flexibility to describe and structure

different kinds of data• It separates data description from data display• It provides a humanly readable format for document

persistence

Where it is Used• The short answer is everywhere

• Ebusiness • Browsers (cdf)• Wireless (wml)• Math (Mathml) , chemistry, biology• Software description (OSD)• Multimedia (SML)• Graphics (SVG)• .Net

How it is Used• Document transference

• Data processing and persistence

• Application messaging

One document Many Outputs

XSLT

Messaging

Messaging

Data Sharing

Soap

Data Persistence

XML provides a data format that is humanly readable if necessary

Even if the originating program is lost or unavailable, it is relatively easy to write a program to parse and access the data from an XML file

A Brief History• SGML ISO standard in 1986• HTML (an SGML application 1990)• 1996 work on a “lite” version of SGML• 1998 XML 1.0 a W3C recommendation• Since then several XML “applications” : XSLT,

XPATH, XLINK, XML Schema, etc.

W3C.org• The World Wide Web Consortium

• http://www.w3c.org

• Levels of specification• Working drafts• Candidate Recommendations• Proposed Recommendations• Recommendations

W3C Goals for XML• XML shall be straightforwardly usable over the

Internet

• XML shall support a variety of applications

• XML shall be compatible with SGML

• It shall be easy to write programs that process XML

Goals Continued• The number of optional features in XML is to be

kept to a minimum, ideally zero

• XML documents should be humanly legible and reasonably clear

• XML design should be prepared quickly

Goals Continued• The design of XML should be formal and

concise

• Terseness in XML markup is of minimal importance

• XML documents shall be easy to create

XML Compared to HTML• HTML

• Pre-established set of elements

• Mixes display with structure

• Loose and forgiving syntax

• Ascii• Case insensitive

• XML• Extensible (open) set of

elements• Separates display from

structure• Strict syntactical structure• Unicode• Case sensitive

XML 1.1• A new recommendation for the XML core

standard was issued in February 2004.

• Because of changes in Unicode, XML names were changed so that everything that is not forbidden is allowed (was only what was specified was allowed)

XML 1.1 continued• New characters added for compatibility with

IBM mainframes, and Unicode.

• Not major changes, but does change the definition of “well-formed” so the new standard was developed.