Schema Instance why does xmlns attribute causes problem?

Hello,

I have a quick question.  I'm trying to validate an XML document using
a Schema and I ran into an issue.  I can't tell, based on the  
specification
why what I have appears invalid.

I have the following:

<test test_id="1"
     xmlns="http://people.rit.edu/~jjp1820/770/project/xtml_test"
     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
     xsi:schemaLocation="http://people.rit.edu/~jjp1820/770/project/xtml_test
                         http://people.rit.edu/~jjp1820/770/project/xtml_test.xsd 
">

Which appears invalid in the tool that I'm using.

But, Once I remove the plain xmlns attribute and get the following
which appears valid:

<test test_id="1"
     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
     xsi:schemaLocation="http://people.rit.edu/~jjp1820/770/project/xtml_test
                         http://people.rit.edu/~jjp1820/770/project/xtml_test.xsd 
">

I would like to know why the top, previous example is "invalid."  To me,
it means the exact same thing, but its slightly redundant.  I will  
certainly
use the bottom from now on, but I would be interested in knowing
how, why, or even if the top syntax is invalid.

Thanks guys,
Joseph Pecoraro