what is the significance of namespaces in xml?

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what is the significance of namespaces in xml?..

Answer / g.h

The true name of an XML element or attribute is not just the
string you see in its text form. It actually consists of
that "local" name combined with the namespace URI. This
combination forms the "qualified name".

Take a look at the following two XML extracts:

<quantity>5</quantity>

<edi:quantity
xmlns:edi='http://ecommerce.example.org'>5</edi:quantity>

Both are "quantity" elements. Both have the same content.
However, the second element is defined within a namespace
scope. Its fully qualified name consists of the namespace
URI (http://ecommerce.example.org) and the local name
(quantity). Mind that the "edi" prefix is of no consequence;
it only serves to bind the element to the namespace.

If both these elements were used in the same XML document,
they would in fact not be equivalent. Namespaces can serve
to create elements with the same local names but with a
different meaning. This is important when mixing XML data
from different contexts, while the meaning of each part must
be maintained.

An example of such a mixed environment is XML embedded in
web pages. Suppose we created a page in XHTML. A part of
this page might consist of an XML document, perhaps with its
own associated stylesheet. Suppose that XML document
contained an element with local name "table". If the web
browser used to view the page just read all markup it
recognized, it would try to interpret that element as a HTML
table. However, in the context of the XML document, the
table tag might have a totally different meaning. It might
in fact model a database table.

A way to solve this would be to use the XHTML namespace as
the default namespace for the web page. The XML document
could then explicitly use the XML namespace. An XHTML and
XML compliant web browser would then only interpret the
elements in the XHTML namespace as HTML markup, using only
these to format the page. The XML document would be handled
in its own way, possibly using a stylesheet.

In short, namespaces are used to allow different XML
vocabularies to be mixed without creating conflicts of meaning.

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