code: public TafResp validate(LifeForm reading, String... info) {
  		TafResp tresp,firstTryAuth=null;
  		for(Taf taf : tafs) {
  			tresp = taf.validate(reading, info);
  			switch(tresp.isAuthenticated()) {
  				case TRY_ANOTHER_TAF:
  					break;
  				case TRY_AUTHENTICATING:
  					if(firstTryAuth==null)firstTryAuth=tresp;
  					break;
  				default:
  					return tresp;
  			}
  		}
  
  		// No TAFs configured, at this point.  It is safer at this point to be "not validated", 
  		// rather than "let it go"
  		return firstTryAuth == null?NullTafResp.singleton():firstTryAuth;
  	}
docs: validate
  
  Respond with the first TAF to authenticate user based on variable info and "LifeForm" (is it
  a human behind an interface, or a server behind a protocol).
  
  If there is no TAF that can authenticate, respond with the first TAF that suggests it can
  establish an Authentication conversation (TRY_AUTHENTICATING).
  
  If no TAF declares either, respond with NullTafResp (which denies all questions)