Instance

XS is the first language (that I know of) that acknowledges that instances may exist outside of the code (coming, for example, from data). the instance keyword allows the programmer to improve such instances. The syntax:

instance Qualified_ID [: type] { ... }

Qualified_ID:

The path to the desired instance, it might be qualified or not, for instance:

instance btnOk
{
    on click(x, y)
    {
    }
}

or

instance control1.btnOk
{
    ...
} 

type:

This feature is not implemented and might not ever be