@Override
	public boolean isConflict(Estimation another) {
		boolean ret = false;
		
		//for example: >=9 VS <=8
		if ((this.getOperType() == GREAT_EQUAL)
				&& (another.getOperType() == LESS_EQUAL)) {
			if (this.getValue() > another.getValue()) {
				ret = true;
			}
		}
		else {
			//for example: <=8 VS >=9
			if ((this.getOperType() == LESS_EQUAL) 
					&& (another.getOperType() == GREAT_EQUAL)) {
				if (this.getValue() < another.getValue()) {
					ret = true;
				}
			}
		}
		return ret;
	}