function subset (super, sub : Trace_Attribute_Set) return Boolean;
function trace_or (a, b : Trace_Attribute_Set) return Trace_Attribute_Set;
function trace_num (tlevel : Trace_Attribute_Set) return String;
function tracetrace (tlevel : Trace_Attribute_Set) return String;
function subset (super, sub : Trace_Attribute_Set) return Boolean;
function trace_or (a, b : Trace_Attribute_Set) return Trace_Attribute_Set;
function trace_num (tlevel : Trace_Attribute_Set) return String;
function tracetrace (tlevel : Trace_Attribute_Set) return String;