custrom svg attributes?

Hi,

   I was wondering if anyone could tell me if it is allowed to make custom svg attributes?
For example, "myatt":

<g id="first_group">
         <text x="180" y="190" id="TestText" myatt="abc" textlength="109">some text</text>
</g>
 
I didn't see anything to confirm this in the svg spec, mailing lists, searches, etc.
   I tried it using the Adobe plug-in for Internet Explorer and it opened without a problem
but I would like to know if it is somehow 'officially' allowed, or does one have to make a
local, custom SVG DTD in order to avoid any obscure problems.  In the end I will be
displaying the svg with Batik/Java and would like to add some element related data
as an attribute.

-Randy