how to recognise other xml files

Hello,

i have a brief question about recognizing files with the extension .xxx as
xml files. Basically i would like to provide a FileLoader for .xxx with the
following capabilities:

1) it should display .xxx files with their own custom icon, not the standard
xml icon in the explorer.

2) it should provide the standard xml actions, plus a set of custom actions
which are only applicable to .xxx files.

3) it should allow browsing of the xml content of the .xxx files in the
explorer, and provide the standard tree-editor for these, so that the tree
can be viewed in the explorer.

some pointers in the right directions would be greately appreciated, i.e.
what classes to look at, or a possible scheme for the achievement of the
stated goals.

best

Val.