namespace

1. IT6801
SERVICE ORIENTED
ARCHITECTURE
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2. UNIT I INTRODUCTION TO XML
XML document structure – Well formed and valid
documents – Namespaces – DTD – XML Schema
– X-Files.

3. XML Namespaces
Provide a method
to avoid element name conflicts

4. XML Namespaces
• Multiple XML developers may choose the same element & attribute names
for their standards
– Each of them, may mean entirely different things.
• For a processing application, to understand & associate the correct elements,
– It must know which tag set the elements come from.
• XML Namespaces provide a method to avoid element name
conflicts.
• Namespaces use a colon-delimited prefix
To associate external semantics with elements
– That can be identified via a Universal Resource Identifier (URI).

5. Example on XML Namespaces
• For instance, this XML carries HTML table information :
• Now, let’s look at another sample XML document
– This XML carries information about a table (a piece of furniture):
<table>
<name>African Coffee Table</name>
<width>80</width>
<length>120</length>
</table>
<table>
<tr>
<td>Apples</td>
<td>Bananas</td>
</tr>
</table>

6. • If these XML fragments were added together,
– There would be a name conflict.
• Both contain a <table> element,
– But the elements have different content and meaning.
• By using namespaces,
– XML parsers can easily tell the difference b/w the two <table> elements.
<h:table>
<h:tr>
<h:td>Apples</h:td>
<h:td>Bananas</h:td>
</h:tr>
</h:table>
<f:table>
<f:name>African Coffee Table</f:name>
<f:width>80</f:width>
<f:length>120</f:length>
</f:table>
In this example,
there will be no conflict
because the two <table>
elements have different
names.

7. Declaring Namespaces
• Namespaces can be declared using one of two methods:
1. A default declaration or
2. An explicit declaration.

8. A Default Declaration
• A default namespace declaration
Specifies a namespace to use for all child elements of the current element
– That do not have a namespace prefix associated with them
• Example :
<Customer xmlns=”http://www.eps-software.com/po”>
<Name>Travis Vandersypen</Name>
<Order>
<Product>
<Name>Hot Dog Buns</Name>
</Product>
</Order>
</Customer>
Default declaration for the <Customer> element is defined
by using the xmlns attribute
All child elements of <Customer> element are
specified as belonging to the
“http://www.eps-software.com/po” namespace

9. An Explicit Declaration
• This is similar to a default namespace declaration,
– Except a prefix is associated with the xmlns attribute.
• Example : A prefix “po” is with the elements within the document:
<cust:Customer xmlns:cust=“http://www.eps-software.com/customer”
xmlns:ord=“http://www.eps-software.com/order”>
<cust:Name>Travis Vandersypen</cust:Name>
<ord:Order>
<ord:Product>
<ord:Name>Hot Dog Buns</ord:Name>
</ord:Product>
</ord:Order>
</cust:Customer>
Two different namespaces are referenced:
one for customers and one for orders.
This allows a different set of rules to be applied for
customer names versus product names.

10. Identifying the Scope of Namespaces
• By default,
– All child elements within a parent element appear within the parent’s namespace.
• This allows
– All child elements to “inherit” their parent element’s namespace.
• The “inherited” namespace can be overwritten
– By specifying a new namespace on a particular child element.

11. Identifying the Scope of Namespaces
• Example:
• <Customer> element declares a default namespace
• <Order> element also declares a default namespace.
• All unqualified elements within the <Order> element will inherit the namespace
declared by the <Order> element.
<Customer xmlns=“http://www.eps-software.com/customer”>
<Name>Travis Vandersypen</Name>
<Order xmlns=“http://www.eps-software.com/order”>
<Product>
<Name>Hot Dog Buns</Name>
</Product>
</Order>
</Customer>