W3C home > Mailing lists > Public > xmlschema-dev@w3.org > March 2007

Re: schemaLocation

From: <noah_mendelsohn@us.ibm.com>
Date: Tue, 20 Mar 2007 10:42:50 -0400
To: "Mystra x64" <mystra_x64@fastmail.fm>
Cc: "George Cristian Bina" <george@oxygenxml.com>, xmlschema-dev@w3.org
Message-ID: <OFB22893C4.FC8DEEEA-ON852572A4.0050376B-852572A4.0050D38E@lotus.com>
Mystra x64 writes:

> Indeed, but isn't names started with 'xml' are reserved? so, 
> namespace:xmlSchemaLocation would work. 

No, they are not.  I suggest that when making assertions like this you 
check the pertinent specifications first, as that holds down the spread of 
misinformation.  What you're thinking of is the fact that element and 
attribute names beginning with xml are reserved in the XML Recommendation 
[1].  That's true.  What you're claiming is that local parts of qualified 
names are also reserved.  That's not true.  From [2]:

---------
Namespace constraint: Reserved Prefixes and Namespace Names

The prefix xml is by definition bound to the namespace name 
http://www.w3.org/XML/1998/namespace. It MAY, but need not, be declared, 
and MUST NOT be undeclared or bound to any other namespace name. Other 
prefixes MUST NOT be bound to this namespace name, and it MUST NOT be 
declared as the default namespace. 

The prefix xmlns is used only to declare namespace bindings and is by 
definition bound to the namespace name http://www.w3.org/2000/xmlns/. It 
MUST NOT be declared or undeclared. Other prefixes MUST NOT be bound to 
this namespace name, and it MUST NOT be declared as the default namespace. 
Element names MUST NOT have the prefix xmlns. 

All other prefixes beginning with the three-letter sequence x, m, l, in 
any case combination, are reserved. This means that: 
users SHOULD NOT use them except as defined by later specifications
processors MUST NOT treat them as fatal errors.

Though they are not themselves reserved, it is inadvisable to use prefixed 
names whose LocalPart begins with the letters x, m, l, in any case 
combination, as these names would be reserved if used without a prefix. 
----------

The emphasis on the last paragraph is mine.  Use of LocalParts beginning 
with xml is discouraged, but they are quite clearly not reserved.  If a 
Recommendation like XML Schema assigned them a meaning in a namespace not 
controlled by the W3C, that would be an error IMO.

Noah

[1] http://www.w3.org/TR/REC-xml/#dt-name
[2] http://www.w3.org/TR/xml-names11/#xmlReserved

--------------------------------------
Noah Mendelsohn 
IBM Corporation
One Rogers Street
Cambridge, MA 02142
1-617-693-4036
--------------------------------------
Received on Tuesday, 20 March 2007 14:43:02 UTC

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