Introduction to XML

1
Introduction to XML

• Chapter 1

2
Chapter Objectives -1

• Discuss markup language
• List and explain drawbacks of HTML
• Discuss the architecture of XML documents
• List the benefits of XML
• Discuss Parser

3
Chapter Objectives -2

• Build a complete XML Document
• Character Data
• Comments
• Processing Instructions
• Entities
• General Entities
• Parameter Entities
• The DOCTYPE Declarations

4
History of Markup
Documents recorded using paper and pen
Typesetters formatting documents
Tools used by typesetters to format a document
5
Markup Language

• A Markup language defines the rules that help to
  add meaning to the content and structure of
  documents.
• They are classified as
• Stylistic Markup It determines the presentation
  of the document
• Structure Markup It defines the structure of
  the document
• Semantic Markup It determines the content of
  the document

6
SGML

• Generalized Markup Language (GML) is the system
  of formatting documents.
• GML was fine-tuned and came to be known as
  Standard Generalized Markup Language (SGML).
• SGML is the source of origin of all markup
  languages

7
Features of SGML

• It describes markup language, which allows
  authors to create their own tags that relate to
  their content.
• It needs a separate file that will contain all
  the rules for the language, for its
  interpretation
• A SGML application is markup language derived
  from SGML.

8
HTML

• HTML is the most famous markup language derived
  from SGML.
• It was created to mark up technical papers so
  that they could be transferred across different
  platforms for the scientific community.
• It is now also used by those non-scientific users
  who are concerned about their documents
  presentation.

9
Drawbacks of HTML

• Fixed tag set
• Presentation technology does not relate to the
  contents
• It is flat
• Clogging
• HTML is not international
• Data interchange is impossible
• Does not have a robust linking mechanism
• HTML is not reusable

10
HTML and XML code Examples
XML Code
HTML Code

• • TOM CRUISE
  • • CLIENT ID 100
    • COMPANY XYZ Corp.
    • Email tom_at_usa.net
    • Phone [phone]
    • Street Adress 25th St.
    • City Toronto
    • State Toronto
    • Zip 20056

• TOM CRUISE
• 100
• XYZ Corp.
• tom_at_usa.net
• 3336767
• 25th St.
• Toronto
• Toronto
• 20056

11
XML -1

• XML stands for Extensible Markup Language.
• It overcomes all the drawbacks of HTML.
• It allows the user to define their own set of
  tags, and also makes it possible for others to
  understand it.
• It is more flexible than HTML.
• It inherits the features of SGML and combines it
  with the features of HTML.
• It is a smaller version of SGML.

12
XML -2

• XML is a metalanguage and it describes other
  languages.
• The data contained in an XML file can be
  displayed in different ways.
• It can also be offered to other applications for
  further processing.
• Style sheets help transform structured data into
  different HTML views. This enables data to be
  displayed on different browsers.

13
XML Architecture - 1

• XML supports three-tier architecture for handling
  and manipulating data.
• It can be generated from existing databases using
  a scalable three-tier model.
• XML tags represent the logical structure of data
  that can be interpreted and used in various ways
  by different applications.
• The middle-tier is used to access multiple
  databases and translate data into XML.

14
XML Architecture -2
15
XML A Universal data format

• HTML is a single markup language, but XML is a
  family of markup languages.
• Any type of data can be easily defined in XML.
• XML is popular because it supports a wide range
  of applications and is easy to use.
• XML has a structured data format, which allows it
  to store complex data

16
Benefits of XML

• The three-tier architecture has easier
  scalability and better security.
• The benefits of XML are classified into the
  following
• Business benefits
• Technological benefits

17
Business Benefits

• Information sharing
• Allows businesses to define data formats in XML
• Provides tools to read, write and transform data
  between XML and other formats
• XML inside a single application
• Powerful, flexible and extensible language
• Content Delivery
• Supports different users and channels, like
  digital TV, phone, web and multimedia kiosks

18
Technological Benefits
Separation of data and presentation
Extensibility
Technological Benefits
Semantic information
Re-use of data
19
XML Advantages

• Eases information exchange
• License free
• Platform independence
• Output format independence
• Application independence
• Built-in internationalization
• No fixed set of markup tags

20
XML Document Structure

• An XML document is composed of sets of entities
  identified by unique names.
• All documents begin with a root or document
  entity.
• Entities are aliases for more complex functions.
• Documents are logically composed of declarations,
  elements, comments, character references, and
  processing instructions.

21
Well formed and Valid Documents

• An XML document is considered as well formed, if
  a minimum set of requirements defined in the XML
  1.0 specification are satisfied.
• The requirements ensure that correct language
  terms are used in the right manner .
• A valid XML document is a well-formed XML
  document, which conforms to the rules of a
  Document Type Definition (DTD).
• DTD defines the rules that an XML markup in the
  XML document must follow.

22
Parsers - 1

• Parsers help the computer interpret an XML file.
• Their are two types of parsers
• Non Validating parser
• Validating parser

23
Parsers - 2
Data tree
24
Creating an XML Document

• To create an XML document
• State an XML declaration
• Create a root element
• Create the XML code
• Verify the document

25
Stating an XML Declaration

• Syntax

encodingUTF-8?

• Standalone and encoding attributes are
  optional, only the version number is mandatory
• Standalone is the external declaration
• Encoding - specifies the character encoding
  used by the author
• XML 1.0 version is default

26
Creating a Root Element

• There can only be one root element
• It describes the function of the document
• Every XML document must have a root element

Example encodingUTP-8?
27
Creating the XML Code

• It is the process of creating our own elements
  and attributes as required by our application.
• Elements are the basic units of XML content.
• Tags tell the user agent to do something to the
  content encased between the start and end tag.

Opening Tag Content Closing Tag

Aptech Ltd
Parts of an element
Element
28
Comments

• This is information for the understanding of the
  user, and is to be ignored by the processor.
• Syntax

The example given will display only the name TOM
CRUSIE, and others are treated as comments.
Example TOM
CRUISE
29
Processing Instruction

• A processing information is a bit of information
  meant for the application using the XML document.
• These instructions are directly passed to the
  application using the parser.
• The XML declaration is also a processing agent.

Instruction information
Name of application
30
Character Data

• The text between the start and end tags is
  defined as character data.
• Character data may be any legal (Unicode).
• Character data is classified into
• PCDATA
• CDATA

31
PCDATA

• It stands for parsed character data.
• PCDATA is text that will be parsed by a Parser.
• Tags inside the text will be treated as markup
  and entities will be expanded.

Predefined entities
 
32
CDATA

• It means character data.
• It will not be parsed by the Parser.
• CDATA are used to make it convenient to include
  large blocks of special characters.
• The character string is not allowed within a
  CDATA block as it will signal the end of the
  CDATA block.

TOM
CRUISE tom_at_usa.com

Example
33
Entities

• Entities are used to avoid typing long pieces of
  text repeatedly within a document.
• There are two categories of entities
• General entities
• Syntax
• by an entity"
• Parameter entities
• Syntax
• represented by an entity"

34
Examples of Entities

• An example of Parameter entities
• QUANTITY "15"
• Entity declaration
• Syntax
• PARAMETER_ENTITY_NAME
• Example
• address

• An example of a General entity
• Suite 12 Paris, France"
• Entity declaration
• Syntax
• ENTITY_NAME
• Example
• address

35
The DOCTYPE declarations

• The declaration follows the XML
  declaration in an XML document.
• Syntax
• ...declare the entities here....
• ...body of the document....

Example firstFloor "15 Downing St Floor 1" secondFloor "15 Downing St Floor 2" thirdFloor "15 Downing St Floor 3"
36
Attributes

• An attribute gives information about an element.
• Attributes are embedded in the element start tag.
• An attribute consists of an attribute name and
  attribute value.

Example SONY count"10"IBM
37
XML Well-formed rules

• All XML elements must have a closing tag
• XML tags are case sensitive
• All XML elements must be properly nested
• All XML documents must have a root element
• Attribute values must always be quoted

38
XML Element Naming

• Names can contain letters, numbers, and other
  characters
• Names must not start with a number or punctuation
  character
• Names must not start with the letters xml (or XML
  or Xml ..)
• Names cannot contain spaces