This combination, including a modifiable parameter, allows you to define the direction of the transformation.
这个组合，包括可修改的参数，使你能够定义转换的方向。
2
The name of the parameter doesn't matter, because it is ignored during transformation, but it is better to select a name that properly identifies it as an exception being thrown.
在转换过程中，参数名是可以被忽略的，但最好还是定义一个合适的名称（以备异常抛出时正确提示）。
3
For example, the toUpper service takes a single parameter named operand and returns the upper case transformationof the resource identified by the URI supplied as the argument.