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BOOK: Beginning XML, 4th Ed ISBN: 978-0-470-11487-2
This is the forum to discuss the Wrox book Beginning XML, 4th Edition by David Hunter, Jeff Rafter, Joe Fawcett, Eric van der Vlist, Danny Ayers, Jon Duckett, Andrew Watt, Linda McKinnon; ISBN: 9780470114872
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Old May 10th, 2011, 12:30 PM
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Default In what namespace(s) are these attributes defined?



<?xml version="1.0" encoding="utf-8" ?>
<contacts xmlns:prefixA="http://localhost/URI_A" xmlns:B="http://localhost/URI_B" ... >
a) In what namespace is xmlns attribute defined and why don't we have to specify this namespace via schemaLocation/xmlns attributes?

b) Are xmlns:prefixA and xmlns:prefixB attributes defined in the same namespace as xmlns attribute?

c) Is the name of the attribute xmlns:prefixA or just prefixA?

2) An element is defined within an XML Schema (XSD) using <element> element. <element> can contain attributes such as name, type, ref, form, minOccurs, maxOccurs, default and fixed. In what namespace are these attributes declared?

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Old May 11th, 2011, 06:21 AM
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My answers may not be 100% technically correct but:
(a) the xmlns namespace is built-in to XML processors so you don't have to define them yourself. I'm not sure if it has a URI associated with it but I have sometimes seen http://www.w3.org/2000/xmlns/ specified, I think this also applies to part b of your question.

It doesn't count as an attribute though, it's a way of defining namespaces in your document so the answer to (c) is neither.

For question 2 XML schemas normally use the prefix xs or xsd and this is bound to the http://www.w3.org/2001/XMLSchema URI. However attributes only usually reside in a namespace is they have a prefix, they don't assume the default namespace as elements can. So the attributes you quote don't have an associated namespace URI.
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Old May 11th, 2011, 03:55 PM
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I'm also learning Linq to XML and I did a bit of searching and found the following quote:

When you declare namespaces, the namespace attributes themselves are in the xmlns namespace. The W3C standard specifies that this namespace does not have to be declared as an attribute in the XML tree. It is a reserved namespace that is always automatically available in the XML parser.
... To create an attribute that declares a namespace with a prefix, you create an attribute where the name of the attribute is the namespace prefix, and this name is in the Xmlns namespace.

Do according to the above quote only the xmlns "attributes" with prefixes ( such as xmlns:prefixA) live in Xmlns namespace, or does xmlns "attribute" itself ( thus xmlns=«...« ) also live in a Xmlns namespace?

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