Studying XAML now, I keep seeing XAML tags in the format Object.Attribute. For example:
OutOfBrowserSettings Sh
As far as I know, there's no specific significance for the '.' in XML. In other words, is a different and unrelated tag from . The relationship in XAML is a semantic understood by the XAML parser only.
On a separate note, the snippet in your question is not XAML; it's part of the deployment manifest for a Silverlight application. Again, though, the semantic of the '.' is understood by the manifest parser, not the XML parser.