@Override
	public String toString() {
		String rslt = getId() + " " + op + " ";
		if (target != null) {
			rslt += target + " ";
		} else if (lValue != null) {
			rslt += lValue + " ";
		} else if (src != null || rValue != null) {
			throw new IllegalStateException("the src is not null, but the target is null");
		}

		if (src != null) {
			rslt += src;
		} else if (rValue != null) {
			rslt += rValue;
		}
		return rslt;
	}