Introduction to XML

1
Introduction to XML
Chapter 1

Core XML / Chapter 1 / Slide 2 of 352
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

Chapter Objectives -2
 Build a complete XML Document:
 Character Data
 Comments
 Processing Instructions
 Entities
 General Entities
 Parameter Entities
 The DOCTYPE Declarations

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

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

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

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.

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 document’s presentation.

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

HTML and XML code Examples
<UL>
<LI> TOM CRUISE
<UL>
<LI> CLIENT ID : 100
<LI> COMPANY : XYZ Corp.
<LI> Email : tom@usa.net
<LI> Phone : 3336767
<LI> Street Adress: 25th
St.
<LI> City : Toronto
<LI> State : Toronto
<LI> Zip : 20056
</UL>
</UL>
<Details>
<CONTACT>
<PERSON_NAME>TOM CRUISE
</PERSON_NAME>
<ID> 100 </ID>
<Company>XYZ Corp. </Company>
<Email> tom@usa.net</Email>
<Phone> 3336767 </Phone>
<Street> 25th St. </Street>
<City> Toronto </City>
<State> Toronto </State>
<ZIP> 20056 </ZIP>
</CONTACT>
</Details>
HTML Code XML Code

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 (people or programs) 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.

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.

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.

XML Architecture -2

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

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

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

Technological Benefits
Technological
Benefits
Re-use of data
Separation of data and
presentation
ExtensibilitySemantic
information

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.

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.

Parsers - 1
 Parsers help the computer interpret an XML
file.
<?xml
version=“1.0”?
>
<nxn>
</nxn>
Editor with the
XML document
Parsed document
viewed in the browser
XML document parsed by the
parser
Their are two types of parsers:
Non Validating parser
Validating parser

Parsers - 2
XML
file
Other related
files (like DTD
file)
Parsers load the XML
and other related files
to check whether the
XML document is well
formed and valid
Data tree

Data versus Markup
<NAME> Tom Cruise </NAME>
Markup
Data

Creating an XML Document
 To create an XML document:
 State an XML declaration
 Create a root element
 Create the XML code
 Verify the document

Stating an XML Declaration
 Syntax
<?xml version=“1.0” standalone=“no” encoding=“UTP-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

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
<?xml version=“1.0” standalone=“no” encoding=“UTP-8”?>
<BOOK>
</BOOK>

Creating the XML Code -1
 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
<TITLE> Aptech Ltd </TITLE>
Element
Parts of an
element

Creating the XML Code -2
 Rules govern the elements:
 At least one element required
 XML tags are case sensitive
 End the tags correctly
 Nest tags Properly
 Use legal tags
 Length of markup names
 Define Valid Attributes

Verify the document
 The document should follow the
XML rules; otherwise it will not be
read by the browser or by any other
XML reader

Comments
 This is information for the understanding of
the user, and is to be ignored by the
processor.
 Syntax
<!- - Write the comment here -- >
Example

<NAME>TOM CRUISE</NAME>
The example given will
display only the name TOM
CRUSIE, and others are
treated as comments.

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.
<?xml:stylesheet type=“text/xsl”?>
Name of application Instruction information

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

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.
Entity Name Character
< <
> >
& &
" "
' '
Predefined entities

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.
<SAMPLE>
<![CDATA[<DOCUMENT>
<NAME>TOM CRUISE</NAME>
<EMAIL>tom@usa.com</EMAIL>
</DOCUMENT>]]>
</SAMPLE>
Example

Entities
 Entities are used to avoid typing long pieces of text
repeatedly within a document.
 There are two categories of entities:
 General entities
Syntax
<!ENTITY ADDRESS "text that is to be represented
by an entity">
 Parameter entities
Syntax
<!ENTITY % ADDRESS "text that is to be represented by an entity">

Examples of Entities
An example of Parameter entities
< CLIENT = "&APTECH;" PRODUCT
= "&PRODUCT_ID;" QUANTITY
= "15">
 Entity declaration
 Syntax
%PARAMETER_ENTITY_NAME
;
 Example
%address;
An example of a General entity
<!ENTITY full_address " My
Address 12 Tenth Ave. Suite 12
Paris, France">
 Entity declaration
 Syntax
&ENTITY_NAME;
 Example
&address;

The DOCTYPE declarations
 The <!DOCTYPE [..]> declaration follows the XML
declaration in an XML document.
 Syntax
<?xml version="1.0"?>
<!DOCTYPE myDoc [
...declare the entities here....
<myDoc>
...body of the document....
</myDoc>
Example
<!DOCTYPE CUSTOMERS [
<!ENTITY firstFloor "15 Downing St Floor 1">
<!ENTITY secondFloor "15 Downing St Floor 2">
<!ENTITY thirdFloor "15 Downing St Floor 3">
]>

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
<TV count="8">SONY</TV>
<LAPTOP count="10">IBM</LAPTOP>

Summary-1
 A markup language defines a set of rules that adds
meaning to the content and structure of documents
 XML is extensible, which means that we can define our
own set of tags, and make it possible for other parties
(people or programs) to know and understand these tags.
This makes XML much more flexible than HTML
 XML inherits features from SGML and includes the
features of HTML. XML can be generated from existing
databases using a scalable three-tier model. XML-based
data does not contain information about how data should
be displayed
 An XML document is composed of a set of “entities”
identified by unique names

Summary-2
 A well-formed document is one that conforms to the basic
rules of XML; a valid document is a well-formed
document that conforms to the rules of a DTD (Document
Type Definition)
 The parser helps the computer to interpret an XML file
 Steps involved in the building of an XML document are:
 Stating an XML declaration
 Creating a root element
 Creating the XML code
 Verifying the document
 Character data is classified into PCDATA and CDATA

Summary-3
 Entities are used to avoid typing long pieces of text repeatedly
in a document. The two types of entities are:
 General entities
 Parameter entities
 The <!DOCTYPE […]> declaration follows the XML
declaration in an XML document.
 An attribute gives information about an element

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