Xml sasidhar

K.Sasidhar
What is XML?What is XML?
 XML stands for EXtensible Markup
Language
 XML is a markup language much like
HTML
 XML was designed to carry data, not to
display data
 XML tags are not predefined. You must
define your own tags
 XML is designed to be self-descriptive
 XML is a W3C Recommendation

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The Difference Between XML andThe Difference Between XML and
HTMLHTML
 XML is not a replacement for HTML.
 XML and HTML were designed with
different goals:
 XML was designed to transport and
store data, with focus on what data is
 HTML was designed to display data,
with focus on how data looks
 HTML is about displaying information,
while XML is about carrying information.
 XML was created to structure, store,
and transport information.
 XML language has no predefined tags

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Differences continue….Differences continue….
 XML is used to transport data, while
HTML is used to format and display the
data.
 XML is a software- and hardware-
independent tool for carrying information.
 With XML You Invent Your Own Tags
 XML is a W3C Recommendation

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Facts of XMLFacts of XML
 XML Separates Data from HTMLXML Separates Data from HTML
 If you need to display dynamic data in yourIf you need to display dynamic data in your
HTML document, it will take a lot of work toHTML document, it will take a lot of work to
edit the HTML each time the data changes.edit the HTML each time the data changes.
 With XML, data can be stored in separateWith XML, data can be stored in separate
XML files. This way you can concentrate onXML files. This way you can concentrate on
using HTML/CSS for display and layout,using HTML/CSS for display and layout,
and be sure that changes in the underlyingand be sure that changes in the underlying
data will not require any changes to thedata will not require any changes to the
HTML.HTML.
 With a few lines of JavaScript code, youWith a few lines of JavaScript code, you
can read an external XML file and updatecan read an external XML file and update
the data content of your web page.the data content of your web page.

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Facts of XMLFacts of XML
 XML Simplifies Data Sharing
 XML data is stored in plain text format.
This provides a software- and hardware-
independent way of storing data.
 This makes it much easier to create
data that can be shared by different
applications.
 XML Simplifies Data Transport
 One of the most time-consuming
challenges for developers is to
exchange data between incompatible
systems over the Internet.

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FACTS OF XMLFACTS OF XML
 XML Simplifies Platform ChangesXML Simplifies Platform Changes
 XML Makes Your Data MoreXML Makes Your Data More
AvailableAvailable
 XML is a meta mark up languageXML is a meta mark up language
that specifies rules for creatingthat specifies rules for creating
markup languagesmarkup languages

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XML DOCUMENT CONTENTXML DOCUMENT CONTENT
 XML Document composed of
 1. Declarations (dtd reference)
 2. Elements
 3. Comments
 4. Entities (Pre-defined, Custom
– defined, character)

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Root StructureRoot Structure

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XML SYNTAXXML SYNTAX
 Syntax is two levels.Syntax is two levels.
 Low level syntax that imposeLow level syntax that impose
rules on all xml documents.rules on all xml documents.
 Other level is either documentOther level is either document
type definition (DTD) or XMLtype definition (DTD) or XML
schemas.schemas.

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XML Syntax Continues….XML Syntax Continues….
 DTDs and schemas specify theDTDs and schemas specify the
set of tags and attributes thatset of tags and attributes that
can appear in a particularcan appear in a particular
document or collection ofdocument or collection of
documents.documents.
 Also specify the order andAlso specify the order and
arrangement in which they canarrangement in which they can
appear.appear.

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XML StatementsXML Statements
 ElementsElements
 Markup declarations areMarkup declarations are
instructions to the xml parser,instructions to the xml parser,
and processing instructions.and processing instructions.

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XML Program structureXML Program structure
 XML declarationXML declaration
 -- identifies the document as XML and provides the-- identifies the document as XML and provides the
version number of XML.version number of XML.
 CommentsComments
 Same as HTMLSame as HTML
 XML namesXML names
 Names are used to name elements and attributes.Names are used to name elements and attributes.
 Names are case sensitiveNames are case sensitive

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ElementsElements
 Root elementRoot element
 Xml document defines a single root element,Xml document defines a single root element,
opening tag and must appear on the first line of theopening tag and must appear on the first line of the
code.code.
 All other elements must be nested inside the rootAll other elements must be nested inside the root
element.element.

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EX. PROGRAMEX. PROGRAM
 <?xml version = “1.0” encoding= “utf-8”?><?xml version = “1.0” encoding= “utf-8”?>
 <ad><ad>
 <year> 2012</year><year> 2012</year>
 <make> Maruthi </make><make> Maruthi </make>
 <model> Alto Lxi </model><model> Alto Lxi </model>
 <color> blue</color><color> blue</color>
 <location><location>
 <city> hyderabad </city><city> hyderabad </city>
 <state> AP </state><state> AP </state>
 </location></location>
 </ad></ad>

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Document Type Definitions
 DTD is a set of structural rules called
declarations.
 DTD Specify the position of a set of
elements.
 DTD Provides entity definitions also.
 DTDs are used when the same tag set
definition is used by a collection of
documents, perhaps by a collection of
users, and the documents must have a
consistent and uniform structure.

K.Sasidhar
DTD
 DTD that embedded with XML is called
internal DTD.
 DTD stored in a separate file is called
external DTD.
 External DTD allows use with more than
one XML document, and are preferable.
 DTD defines the document structure with
a list of legal elements and attributes.

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Internal DTD Example
 <?xml version="1.0"?>
<!DOCTYPE note [
<!ELEMENT note (to,from,heading,body)>
<!ELEMENT to (#PCDATA)>
<!ELEMENT from (#PCDATA)>
<!ELEMENT heading (#PCDATA)>
<!ELEMENT body (#PCDATA)>
]>
<note>
<to>clerk</to>
<from>HOD</from>
<heading>Issue Hall Tickets</heading>
<body>Issue the hall tickets for those who had
required attendance</body>
</note>

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DTD ex: explanation
 The DTD above is interpreted like this:
 !DOCTYPE note defines that the root element of
this document is note
 !ELEMENT note defines that the note element
contains four elements: "to,from,heading,body"
 !ELEMENT to defines the to element to be of
type "#PCDATA"
 !ELEMENT from defines the from element to be
of type "#PCDATA"
 !ELEMENT heading defines the heading element
to be of type "#PCDATA"
 !ELEMENT body defines the body element to be
of type "#PCDATA"

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External DTD declaration ex:
 <!ELEMENT note
(to,from,heading,body)>
<!ELEMENT to (#PCDATA)>
<!ELEMENT from (#PCDATA)>
<!ELEMENT heading
(#PCDATA)>
<!ELEMENT body (#PCDATA)>

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DTD continue….
<!DOCTYPE note SYSTEM "note.dtd">
<note>
<to>clerk</to>
<from>HOD</from>
<heading>Issue Hall Tickets </heading>
<body> Issue the hall tickets for those
who had required attendance </body>
</note>

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XML Building Blocks
 Tags
 Elements
 Attributes
 Entities
 PCDATA (Parsable Character Data)
 CDATA

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Element descriptions
 Suffixes:
? optional
+ one or more
* zero or more
 Separators
, both, in order
| or
 Grouping
( ) grouping

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Empty elements
 <!ELEMENT element-name
EMPTY>
Example:
<!ELEMENT br EMPTY>
XML example:
<br />

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Elements with Parsed Character
Data
 <!ELEMENT from (#PCDATA)>

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Elements with any Contents
 Elements declared with the category
keyword ANY, can contain any
combination of parsable data
 <!ELEMENT element-name ANY>
Example:
<!ELEMENT note ANY>

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Elements with Children
(sequences)
 <!ELEMENT element-name (child1)>
or
<!ELEMENT element-name
(child1,child2,...)>
Example:
<!ELEMENT note
(to,from,heading,body)>

K.Sasidhar
DTD - Attributes
 In a DTD, attributes are declared with an
ATTLIST declaration.
 Syntax:
 <!ATTLIST element-name attribute-name
attribute-type default-value>
 DTD example:
<!ATTLIST payment type CDATA "check">
XML example:
<payment type="check" />

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Attribute types
 The attribute-type can be one of the following:
CDATA The value is character
data
(en1|en2|..) Value from enum list
ID Value is unique id
IDREF Value is id of another
element
IDREFS Value is list of other ids
NMTOKEN Valid xml name
ENTITY Value is an entity
ENTITITES List of entities
notation Value is name of notation
Xml: Value is predefined xml
value

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Elements vs. Attributes
 Data can be stored in child elements
or in attributes.
 <person gender ="male">
<firstname>sravan</firstname>
<lastname>kota</lastname>
</person>
 gender is attribute in this
example.

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Elements vs. Attributes continue..
 <person>
<gender>male</gender>
<firstname>sravan</firstname>
<lastname>kota</lastname>
</person>
 gender is child element in this
example.
 No rules are there when to use
attributes or elements.
 It depends on programmer
 If the programmer feels information is
useful better to use elements.

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Problems with attributes
 attributes cannot contain multiple
values (child elements can)
 attributes are not easily expandable
(for future changes)
 attributes cannot describe structures
(child elements can)
 attributes are more difficult to
manipulate by program code
 attribute values are not easy to test
against a DTD

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ENTITIES
 Entities are variables used to define shortcuts
to standard text or special characters.
 Entities can be declared internal or external
 Internal entity syntax:
 <!ENTITY entity-name "entity-value">
 DTD Example:
<!ENTITY writer "Donald Duck.">
<!ENTITY copyright "Copyright of Disney.">
XML example:
<author>&writer; &copyright;</author>
 Note: entity has 3 parts. &, name and ;

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External Entity Declaration
 Syntax
 <!ENTITY entity-name SYSTEM "URL">
 DTD Example:
<!ENTITY college SYSTEM
"http://www.sreenidhi.com/entities.dtd">
<!ENTITY copyright SYSTEM
"http://www.sreenidhi.com/entities.dtd">
XML example:
<author>&writer;&copyright;</author>
Note: entity has 3 parts. &, name and ;

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Important Keywords in DTD
 #REQUIRED
 #IMPLIED
 #FIXED
 #PCDATA

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DTDs DISADVANTAGES
 DTDs are written in a syntax unrelated to
XML.
 Cannot be analyzed with an xml
processor
 Confusion to deal with two different
syntactic formats ( one to define
document and two to define its structure).
 DTD data types are not numeric.
 With DTDs the content of an element
specified as text even though it could be
an integer, floating-point number or a
range of numbers.

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XML Schema
 XML Schema describes the structure of an
XML document.
 The XML Schema language is also
referred to as XML Schema Definition
(XSD).

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XML Schema Vs DTD
Xml schema DTD
Created by using xml
syntax.
Xml style sheets (XSL) are
used with xml schemas.
Not allowed with xsl
Supports Namespaces No namespaces
Supports more data types
including number and
derived data types
Supports only character
data types
Easy to create and edit
complex content
Difficult to reusable
Xml schema can be
parsable by xml parsers
Cannot parsable

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Use of XML Schema in web design
 Defines root and child elements that
can appear in a document
 Defines attributes that can appear in a
document
 Defines the order and number of child
elements
 Defines whether an element is empty
or can include text
 Defines data types for elements and
attributes
 Defines default and fixed values for
elements and attributes

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XML Schema importance …..
 XML Schemas are extensible to
future additions
 XML Schemas are richer and
more powerful than DTDs
 XML Schemas support data
types and namespaces

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Importance continues…
 XML Schema is an xml
document so it can be parsed
with an xml parser.
 Provides more control over data
types than DTDs.
 XML schemas are namespace
centric.

K.Sasidhar
Fundamentals
 Schemas are like class and
object in oop language.
 Schema is similar to class
definition
 Xml document that conforms to
the structure defined in the
schema is similar to an object of
the schema’s class.

K.Sasidhar
Purposes of schemas
 Have 2 primary purposes.
 First, a schema specifies the structure
of its instance XML documents,
including which elements and
attributes may appear in the instance
document, as well as where and how
often they may appear.
 Second, schema specifies the data
type of every element and attribute of
its instance XML documents.

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Defining a schema
 Every schema has schema as its root
element.
 Schema element specifies the namespace
for the schema of schemas from which the
schema’s elements and attributes will be
drawn.
 Xmlns:xsd = “http://www.w3.org/2001/XMLSchema”

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Ex Program
<?xml version="1.0"?>
<xs:schema
xmlns:xs="http://www.w3.org/2001/X
MLSchema"
targetNamespace="http://www.sreeni
dhi.com"
xmlns="http://www.sreenidhi.com"
elementFormDefault="qualified">
...
...
</xs:schema>

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explanation
 xmlns:xs="http://www.w3.org/2001/X
MLSchema"
 indicates that the elements and data types
used in the schema come from the
"http://www.w3.org/2001/XMLSchema"
namespace. It also specifies that the
elements and data types that come from the
"http://www.w3.org/2001/XMLSchema"
namespace should be prefixed with xs:
 targetNamespace="http://www.sreenidhi.co
m"
 indicates that the elements defined by this
schema (note, to, from, heading, body.)
come from the "http://www.sreenidhi.com"
namespace.

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explanation
 xmlns=http://www.sreenidhi.com
 indicates that the default
namespace is
"http://www.sreenidhi.com".
 elementFormDefault="qualified"
 indicates that any elements used
by the XML instance document
which were declared in this
schema must be namespace
qualified.

K.Sasidhar
XML Schema reference
<note xmlns="http://www.sreenidhi.com"
xmlns:xsi="http://www.w3.org/2001/XMLSc
hema-instance"
xsi:schemaLocation="http://www.sreenidhi.
com note.xsd">
<to>clerk</to>
<from>HOD</from>
<heading>Issue Hall Tickets</heading>
<body> Issue the hall tickets for those who
had required attendance </body>
</note>

K.Sasidhar
Data Types
 Binary: Supports hexa code
 Logic data types: Boolean
 Number data types: Float, double, decimal,
long
 Date and time data types: Time
(hh:mm:ss), duration, date, date time etc..
 Text Data types: URL, string
 XML Data types: Qualified names (qname)

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Facets
 EX: Facets of integer primitive data
type has eight possible facets:
 totalDigits, maxInclusive,
maxExclusive, minInclusive,
minExclusive, pattern, enumeration
and whitespace.
 This list can be found at
 www.w3.org/TR/xmlschema-2/#built-
in-datatypes.

K.Sasidhar
Simple types
 <xsd: element name=“engine”
type = “xsd:string” />
 An instance of schema in which
the engine element is defined
could have the following
element
 <engine> inline six cylinder fuel
injected </engine>

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Ex:
 <xsd: simpletype name=
“firstname”>
 <xsd: restriction base =
“xsd:string”>
 <xsd:maxLength value = “10”/>
 </xsd:restriction>
 </xsd:simpletype>

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Complex types
 <xsd: complexType name = “sports_car”>
 <xsd:sequence>
 <xsd: element name = “make”
type=“xsd:string” />
 <xsd: element name = “model”
 <xsd: element name = “engine”
 <xsd: element name = “year”
type=“xsd:decimal” />
 </xsd:sequence>
 </xsd: complexType>

Xml sasidhar

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