This document provides an introduction and overview of XML. It explains that XML stands for Extensible Markup Language and is used for data transportation and storage in a platform and language neutral way. XML plays an important role in data exchange on the web. The document discusses the history of XML and how it was developed as an improvement over SGML and HTML by allowing users to define their own tags to structure data for storage and interchange. It also provides details on the pros and cons of XML compared to other markup languages.

1. Introduction and Overview of
XML

2. Objectives
• Explain what XML is and the need for XML
• Know other markup languages – SGML, HTML,
XHTML
• Understand the difference between SGML,
HTML and XML
• Know the various applications of XML
• Know the pros and cons of XML

3. XML
• XML stands for Extensible Markup Language.
• XML is a tool for data transportation and data
storage in platform and language neutral way.
• XML plays an important role in the exchange of a
wide variety of data on the web
• XML defines set of rules for encoding documents
which is both human-readable and machine-
readable
• All rules are defined in XML 1.0 specification
developed by W3C an open standard
• Many Parsers or APIs(Application Programming
Interface) are available to process the XML data

4. History of XML
• W3C’s primary goals is to make the Web universally
accessible—regardless of disabilities, language, culture, etc
• Internet is a collection of interconnected computers
• DARPANET (Defense Advanced Research Project Agency
Network) was the first network to interconnect academic,
government and private research organizations
• Initially, internet used for sending electronic messages and
transferring files.
• FTP(File Transfer Protocol) allows people to request files
from the other system
• Limitation
– what format the files requested would be in and
– Can the file be processed

5. Contd.
• CERN browser
– Used to request files over the internet and display
them in a predefined format
– Uses
• HTTP (Hyper Text Transfer Protocol) and
• HTML(Hyper text markup language)
• Presentation details cannot be transferred as they
are coded in the machine specific manner that may
not be understood at the receiving end

6. Contd.
• Standardized Generalized Markup Language (SGML) -
allows information about the document's structure to be
preserved
• DSSSL – Document style semantics and specification
language
• SGML is used to specify mark up languages.
• The purpose of SGML is to create the vocabularies which
could be used to mark up documents with structural tags.
• HTML - one of the most popular applications of SGML
• HTML - mark up language used for presentation i.e. design
a webpage
• HTML - All tags predefined

7. Contd.
• Limitation of HTML
– Data storage and interchange of data is not
possible using HTML
– All tags are predefined
• XML bridges this gap
– human readable, while being flexible enough to
support platform and
– architecture independent data interchange

8. SGML vs HTML vs XML
• HTML allows hypertext links to be specified,
SGML does not allow any hyper text links
• HTML is used for presentation, not the meaning
of the data content,
XML describes the meaning of the document
• HTML is not extensible,
XML is highly extensible

9. Semi Structured Data
• Data may be
– Structured
– Unstructured
– Raw data
• Text Database – Unstructured
• Text Mark Up – Mark-up languages
• SGML – meta language
• HTML – markup language with predefined
tags