Lecture 1 XML Introduction.pptx

7/28/2019 Lecture 1 XML Introduction.pptx

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Introduction


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What is XML Extensible Markup Language.

Extensible: lets you define your own tags, the order in

which they occur, and how they should be processedor displayed.

Markup

Language:

XML is a meta-language: a language that allows us tocreate or define other languages.


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Why Do We Need XML?XML Separates Data from HTML

XML Simplifies Data Sharing

XML Simplifies Data TransportXML Simplifies Platform Changes

XML is Used to Create New Internet Languages


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Example of XML document

ToveJaniReminderDon't forget me this weekend!


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The first line is the XML declaration. It defines theXML version (1.0) and the encoding used (ISO-8859-1= Latin-1/West European character set).

The next line describes the root element of thedocument (like saying: "this document is a note"):

The next 4 lines describe 4 child elements of the root

(to, from, heading, and body)


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XML Documents Form a Tree

StructureXML documents must contain a root element. This

element is "the parent" of all other elements.

The elements in an XML document form a documenttree. The tree starts at the root and branches to thelowest level of the tree.

All elements can have sub elements (child elements)


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XML Documents Form a Tree

Structure

.....

The terms parent, child, and sibling are used todescribe the relationships between elements. Parent

elements have children. Children on the same level arecalled siblings (brothers or sisters).

All elements can have text content and attributes (justlike in HTML).


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XML Syntax RulesAll XML Elements Must Have a Closing Tag

In HTML, some elements do not have to have a closing

tag:

This is a paragraph.

In XML, it is illegal to omit the closing tag. All

elements must have a closing tag

This is a paragraph.


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XML Syntax RulesXML Tags are Case Sensitive

XML tags are case sensitive. The tag is

different from the tag . Opening and closing tags must be written with the

same case

This is incorrect

This is correct "Opening and closing tags" are often referred to as

"Start and end tags".


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XML Syntax RulesXML Elements Must be Properly Nested

In XML, all elements must be properly nested within

each other: This text is bold and italic

XML Documents Must Have a Root Element


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XML Syntax RulesXML Attribute Values Must be Quoted

XML elements can have attributes in name/value pairs

just like in HTML. In XML, the attribute values must always be quoted.

Tove

Jani


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XML Syntax Rules

ToveJani

ToveJani


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XML Syntax Rules Entity References

Some characters have a special meaning in XML.

If you place a character like "


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XML Syntax Rules Entity References There are 5 predefined entity references in XML:

Only the characters "


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XML Syntax Rules Comments in XML

The syntax for writing comments in XML is similar to

that of HTML.


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XML Syntax RulesWhite-space is Preserved in XML

HTML truncates multiple white-space characters to

one single white-space: HTML:Hello Tove

Output:Hello Tove

With XML, the white-space in a document is not

truncated.XML Stores New Line as LF


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XML ElementsAn XML document contains XML Elements.


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What is an XML Element?An XML element is everything from (including) the

element's start tag to (including) the element's endtag.

An element can contain:

other elements

text

attributes or a mix of all of the above...


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What is an XML Element?

Harry PotterJ K. Rowling

200529.99

Learning XML

Erik T. Ray200339.95


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What is an XML Element? In the example above, and

have element contents, because they contain otherelements. also hasan attribute (category="CHILDREN"). ,, , and have textcontent because they contain text.


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XML Naming RulesXML elements must follow these naming rules:

Names can contain letters, numbers, and othercharacters

Names cannot start with a number or punctuationcharacter

Names cannot start with the letters xml (or XML, or

Xml, etc) Names cannot contain spaces

Any name can be used, no words are reserved.


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XML ElementsXML Elements are Extensible

XML elements can be extended to carry moreinformation.

ToveJani

Don't forget me this weekend!


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XML Elements

2008-01-10Tove

JaniReminderDon't forget me this weekend!


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XML AttributesXML elements can have attributes, just like HTML.

Attributes provide additional information about anelement.


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XML Attributes In HTML, attributes provide additional information

about elements:


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XML AttributesXML Attributes Must be Quoted

Attribute values must always be quoted. Either singleor double quotes can be used. For a person's gender,the person element can be written like this:

or like this:


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XML Attributes If the attribute value itself contains double quotes you

can use single quotes, like in this example:

or you can use character entities:


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XML Elements vs. Attributes

AnnaSmith

femaleAnnaSmith


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Avoid XML Attributes? Some of the problems with using attributes are: attributes cannot contain multiple values (elements

can)

attributes cannot contain tree structures (elements can)

attributes are not easily expandable (for future changes)


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XML Attributes for Metadata Sometimes ID references are assigned to elements.

These IDs can be used to identify XML elements inmuch the same way as the id attribute in HTML.


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XML Attributes for Metadata

ToveJani

ReminderDon't forget me this weekend!

Jani

ToveRe: ReminderI will not


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XML ValidationXML with correct syntax is "Well Formed" XML.

XML validated against a DTD is "Valid" XML.


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Well Formed XML DocumentsA "Well Formed" XML document has correct XML

syntax.

The syntax rules were described in the previouschapters:

XML documents must have a root element

XML elements must have a closing tag

XML tags are case sensitiveXML elements must be properly nested

XML attribute values must be quoted


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Valid XML DocumentsA "Valid" XML document is a "Well Formed" XML

document, which also conforms to the rules of aDocument Type Definition (DTD):

Tove

JaniReminderDon't forget me this weekend!


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XML DTD The purpose of a DTD is to define the structure of an

XML document. It defines the structure with a list ofof legal elements:

]>


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XML NamespacesXML Namespaces provide a method to avoid element

name conflicts.

Name Conflicts

In XML, element names are defined by the developer.This often results in a conflict when trying to mix XMLdocuments from different XML applications.


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XML Namespaces This XML carries HTML table information:

ApplesBananas

This XML carries information about a table (a piece of furniture):

African Coffee Table80120


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XML Namespaces If these XML fragments were added together, there

would be a name conflict. Both contain a element, but the elements have different content and

meaning.An XML parser will not know how to handle these

differences.


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XML Namespaces Solving the Name Conflict Using a Prefix: Name conflicts in XML can easily be avoided using a name prefix.

Apples

Bananas


120


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XML Namespaces - The xmlns

AttributeWhen using prefixes in XML, a so-

called namespace for the prefix must be defined.

The namespace is defined by the xmlns attribute inthe start tag of an element.

The namespace declaration has the following syntax.xmlns:prefix="URI"


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Attribute

Apples

Bananas



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Attribute In the previous example, the xmlns attribute in the

tag give the h: and f: prefixes a qualifiednamespace.

When a namespace is defined for an element, all childelements with the same prefix are associated with thesame namespace.

Namespaces can be declared in the elements where

they are used or in the XML root element


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Attribute

Apples

Bananas



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Default Namespaces Defining a default namespace for an element saves us fromusing prefixes in all the child elements. It has the followingsyntax:

xmlns="namespaceURI" This XML carries HTML table information:

ApplesBananas


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XML ParserAll modern browsers have a built-in XML parser.

An XML parser converts an XML document into anXML DOM object - which can then be manipulatedwith JavaScript.


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XML CDATAAll text in an XML document will be parsed by the

parser.

But text inside a CDATA section will be ignored by theparser.


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PCDATA - Parsed Character Data XML parsers normally parse all the text in an XML document.

When an XML element is parsed, the text between the XML tags is alsoparsed: This text is also parsed The parser does this because XML elements can contain other

elements, as in this example, where the element contains twoother elements (first and last):

BillGates and the parser will break it up into sub-elements like this:

BillGates

Parsed Character Data (PCDATA) is a term used about text data that

will be parsed by the XML parser.


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CDATA - (Unparsed) Character

Data The term CDATA is used about text data that should not beparsed by the XML parser.

Characters like "


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CDATA - (Unparsed) Character

Data A CDATA section starts with "":

if (a < b && a < 0) then{return 1;}

else{return 0;}

}]]>


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Quiz 1.What does XML stand for?

A. eXtensible Markup Language

B. X-Markup LanguageC. Example Markup Language

D. eXtra Modern Link


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2.There is a way of describing XML data, how?

A. XML uses a DTD to describe the data

B. XML uses a description node to describe dataC. XML uses XSL to describe data


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3.XML's goal is to replace HTML

False

True


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4. What is the correct syntax of the declarationwhich defines the XML version?

A.

B.

C.


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5.What does DTD stand for?

A. Do The Dance

B. Document Type DefinitionC. Direct Type Definition

D. Dynamic Type Definition


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6. Is this a "well formed" XML document?

ToveJaniReminderDon't forget me this weekend!

Yes No


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8.Which statement is true?

A. All XML elements must be properly closed

B.All XML elements must be lower caseC. All XML documents must have a DTD

D. All the statements are true


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9. Which statement is true?

A. All the statements are true

B.XML tags are case sensitiveC. XML documents must have a root tag

D. XML elements must be properly nested


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10.XML preserves white spacesFalse

True


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11.Is this a "well formed" XML document?

ToveJaniNo

Yes


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12. XML elements cannot be emptyFalse

True


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13. Which is not a correct name for an XML element?

A.

B.

C.

D. All 3 names are incorrect


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14. Which is not a correct name for an XMLelement?

A.

B.

C.



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16.Which is not a correct name for an XML element?

A.

B.

C.



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17.XML attribute values must always be enclosedin quotesFalse

True

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