Class view graphical tool

[Opariti]

Hi,
I'm looking for a graphical output tool able to display a structure of classes - related/linked rectangles having properties (no methods in my case). The technology should be around Silverlight, with input about the boxes and relationships defined in XML format. The tool needs to be able to "appropriately" place the boxes in the screen/page limits.
Don't care if is free software or not, what is important is to provide the functionality above. If possible, not too much more ;-) ...
Thanks!