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Dr Alexiei Dingli

XML Technologies

XML Advanced

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Since XML element names can be defined

by anyone, this often results in a conflict

Such as

How would you add XML related to furniture(tables and chairs) to an HTML document?

Conflicts !!!

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If these XML fragments were added together,

there would be a name conflict

Both contain a element, but theelements have different content and meaning

An XML parser will not know how to handlethese differences

Even more conflicts !!!

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Name conflicts in XML can easily be avoided using a name prefix This XML carries information about an HTML table, and a piece of

furniture:

Apples

Bananas

Coffee Table

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In the example above, there will be no conflict because the two

elements have different names.

Solving conflicts ...

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The namespace is defined by the xmlnsattribute in the start tag of an element

The namespace declaration has the

following syntax

xmlns:prefix="URI"

XML Namespaces

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Apples

Bananas

African Coffee Table

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Namespaces Ex 1

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Apples

Bananas

African Coffee Table

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Namespaces Ex 2

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The xmlns attribute in the tag gave the h: and f: prefixes a

qualified namespace

When a namespace is defined for an element, all child elements with

the same prefix are associated with the same namespace

Namespaces can be declared in the elements where they are used

or in the XML root element

The namespace URI is not used by the parser to look up information

The purpose is to give the namespace a unique name, however,

often companies use the namespace as a pointer to a web page

containing namespace information

More on Namespaces

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XML documents can contain non ASCII

characters, like French .

To avoid errors, specify the XML encoding

Two encoding errors: An invalid character was found in text content.

Switch from current encoding to specified encoding notsupported.

XML Encoding

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Different encodings ...

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DOM (Document Object Model) defines a standard way for

accessing and manipulating documents

Consider XML documents as a tree-structure

All elements can be accessed through the DOM tree

Their content (text and attributes) can be modified or deleted, and

new elements can be created

The elements, their text, and their attributes are all known as nodes

DOM

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x=xmlDoc.getElementsByTagName("title")[0].childNodes[0];

Retrieves the text value of the first element

txt=xmlDoc.getElementsByTagName("title")[0].getAttribute("lang");

retrieves the text value of the "lang" attribute of the first element

Advanced DOM examples

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The CD Catalogue (XML)

The CD Catalogue (Code)

The CD Catalogue (HTML)

XML to HTML

http://localhost/var/www/apps/conversion/tmp/scratch_4/examples/cd_catalog.xmlhttp://localhost/var/www/apps/conversion/tmp/scratch_4/examples/cd_catalogue.txthttp://localhost/var/www/apps/conversion/tmp/scratch_4/examples/cd_catalogue.htmlhttp://localhost/var/www/apps/conversion/tmp/scratch_4/examples/cd_catalogue.htmlhttp://localhost/var/www/apps/conversion/tmp/scratch_4/examples/cd_catalogue.txthttp://localhost/var/www/apps/conversion/tmp/scratch_4/examples/cd_catalog.xml

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We check the browser, and load the XML using the correct parser

We create an HTML table with

We use getElementsByTagName() to get all XML CD nodes

For each CD node, we display data from ARTIST and TITLE as table

data.

We end the table with

XML to HTML explanation

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xmlhttp.open("GET",url,true);

Our examples use "true" in the third parameter of open()

This parameter specifies whether the request should be handled

asynchronously True means that the script continues to run after the send() method,

without waiting for a response from the server

The onreadystatechange event complicates the code. But it is the

safest way if you want to prevent the code from stopping if you don't

get a response from the server. By setting the parameter to "false", your can avoid the extra

onreadystatechange code. Use this if it's not important to execute

the rest of the code if the request fails.

XMLHttpRequest Async

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