make component muteable and add revisionName

Signed-off-by: 天元 <[email protected]>

7.application_configuration.md

@@ -78,11 +78,17 @@ This section defines the instances of components to create with the application
 
 | Attribute | Type | Required | Default Value | Description |
 |-----------|------|----------|---------------|-------------|
-| `componentName` | `string` | Y | | The name of the component of which to create an instance. |
+| `componentName` | `string` | N | | The name of the component of which to bind application configuration. Using componentName represent the ApplicationConfiguration always track the latest revision. |
+| `revisionName` | `string` | N | | The name of the component revision of which to bind application configuration. |
 | `parameterValues` | [`[]ParameterValue`](#parameterValue) | N | | Overrides of parameters that are exposed by the application scope type defined in `type`. |
 | `scopes` | [`[]Scope`](#scope) | N | | The scopes to be used in the component. A component joins a scope by referencing it. |
 | `traits` | [`[]Trait`](#trait) | N | | The traits to attach to this component instance. |
 
+One of `componentName` and `revisionName` is required. Everytime when a component is changed, a component revision will auto-generated by OAM implementation and can be viewed by user.
+
+* Using `componentName` here means the ApplicationConfiguration will always track the latest verison of the component.
+* Using `revisionName` means only the specific revision of component will work, newly changed component version can only work after the `revisionName` is match with the new name.
+
 In addition to being unique, the `componentName` must follow these naming rules:
 
 > The componentName field is required and must be 63 characters or less, beginning and ending with an alphanumeric character ([a-z0-9A-Z]) with dashes (-), underscores (_), dots (.), and alphanumerics between.