function index() {
	var out;
	var id;
	var i;
	out = {};
	for ( i = 0; i < FILES.length; i++ ) {
		// Extract a party abbreviation from a filename:
		id = FILES[ i ].match( RE )[ 3 ];

		// Convert the abbreviation to the full party name:
		id = PARTY[ id ];

		if ( hasOwnProp( out, id ) ) {
			out[ id ].push( i );
		} else {
			out[ id ] = [ i ];
		}
	}
	return out;
}
Generates an index for querying the SOTU database by party.

@private
@returns {Object} database index