The signature of a query Struct or a Primitive
Converts this Signature to Indicator, if possible without loosing information, otherwise throws an exception
Converts this signature to a Struct '/'([name], [arity]) or '/'([name],'+'([arity], vararg))
'/'([name], [arity])
'/'([name],'+'([arity], vararg))
Creates corresponding Struct of this Signature with provided arguments