# Matching Rules of Explicit Want and Implicit Want

Both explicit [Want](../reference/apis/js-apis-app-ability-want.md) and implicit [Want](../reference/apis/js-apis-app-ability-want.md) can be used to match an application component to start based on certain rules. These rules determine how the parameters set in [want](../reference/apis/js-apis-app-ability-want.md) match the configuration file declared by the target application component.

## Matching Rules of Explicit Want


The table below describes the matching rules of explicit [Want](../reference/apis/js-apis-app-ability-want.md).

| Name| Type| Matching Item| Mandatory| Rule Description|
| -------- | -------- | -------- | -------- | -------- |
| deviceId | string | Yes| No| If this field is unspecified, only application components on the local device are matched.|
| bundleName | string | Yes| Yes| If **abilityName** is specified but **bundleName** is unspecified, the matching fails.|
| moduleName | string | Yes| No| If this field is unspecified and multiple modules with the same ability name exist in the application, the first application component is matched by default.|
| abilityName | string | Yes| Yes| To use explicit Want, this field must be specified.|
| uri | string | No| No| This field is not used for matching. It is passed to the target application component as a parameter.|
| type | string | No| No| This field is not used for matching. It is passed to the target application component as a parameter.|
| action | string | No| No| This field is not used for matching. It is passed to the target application component as a parameter.|
| entities | Array<string> | No| No| This field is not used for matching. It is passed to the target application component as a parameter.|
| flags | number | No| No| This field is not used for matching and is directly transferred to the system for processing. It is generally used to set runtime information, such as URI data authorization.|
| parameters | {[key: string]: any} | No| No| This field is not used for matching. It is passed to the target application component as a parameter.|

## Matching Rules for Implicit Want

The table below describes the matching rules of implicit [Want](../reference/apis/js-apis-app-ability-want.md).

| Name       | Type                          | Matching Item| Mandatory| Rule Description                                                        |
| ----------- | ------------------------------ | ------ | ---- | ------------------------------------------------------------ |
| deviceId    | string                         | Yes    | No  | Implicit invoking is not supported across devices.                                  |
| abilityName | string                         | No    | No  | To use implicit Want, this field must be left unspecified.                                |
| bundleName  | string                         | Yes    | No  | - When only **bundleName** is specified, matching is limited to that application.<br>- When both **bundleName** and **moduleName** are specified, matching is limited to that module in that application.<br>- When only **moduleName** is specified, the setting is invalid.<br> <br>These fields will be used for implicit matching.|
| moduleName  | string                         | Yes    | No  |                                                              |
| uri         | string                         | Yes    | No  |                                                              |
| type        | string                         | Yes    | No  |                                                              |
| action      | string                         | Yes    | No  |                                                              |
| entities    | Array&lt;string&gt;            | Yes    | No  |                                                              |
| flags       | number                         | No    | No  | This field is not used for matching and is directly transferred to the system for processing. It is generally used to set runtime information, such as URI data authorization.|
| parameters  | {[key:&nbsp;string]:&nbsp;any} | No    | No  | This field is not used for matching. It is passed to the target application component as a parameter.        |

Get familiar with the following about implicit Want:


- The **want** parameter passed by the caller indicates the operation to be performed by the caller. It also provides data and application type restrictions.

- The **skills** field declares the capabilities of the target application component. For details, see [the skills tag](../quick-start/module-configuration-file.md#skills) in the [module.json5 file](../quick-start/module-configuration-file.md).


The system matches the **want** parameter (including the **action**, **entities**, **uri**, and **type** attributes) passed by the caller against the **skills** configuration (including the **actions**, **entities**, **uris**, and **type** attributes) of the application components one by one. When all the four attributes are matched, a dialog box is displayed for users to select a matched application.


### Matching Rules of action in the want Parameter

The system matches the **action** attribute in the **want** parameter passed by the caller against **actions** under **skills** of the application components.

- If **action** in the passed **want** parameter is unspecified and **actions** under **skills** of an application component is unspecified, the matching fails.

- If **action** in the passed **want** parameter is specified but **actions** under **skills** of an application component is unspecified, the matching fails.

- If **action** in the passed **want** parameter is unspecified but **actions** under **skills** of an application component is specified, the matching is successful.

- If **action** in the passed **want** parameter is specified, and **actions** under **skills** of an application component is specified and contains **action** in the passed **want** parameter, the matching is successful.

- If **action** in the passed **want** parameter is specified, and **actions** under **skills** of an application component is specified but does not contain **action** in the passed **want** parameter, the matching fails.

  **Figure 1** Matching rules of action in the want parameter
![want-action](figures/want-action.png)


### Matching Rules of entities in the want Parameter

The system matches the **entities** attribute in the **want** parameter passed by the caller against **entities** under **skills** of the application components.

- If **entities** in the passed **want** parameter is unspecified but **entities** under **skills** of an application component is specified, the matching is successful.

- If **entities** in the passed **want** parameter is unspecified but **entities** under **skills** of an application component is unspecified, the matching is successful.

- If **entities** in the passed **want** parameter is specified but **entities** under **skills** of an application component is unspecified, the matching fails.

- If **entities** in the passed **want** parameter is specified, and **entities** under **skills** of an application component is specified and contains **entities** in the passed **want** parameter, the matching is successful.

- If **entities** in the passed **want** parameter is specified, and **entities** under **skills** of an application component is specified but does not contain **entities** in the passed **want** parameter, the matching fails.

  **Figure 2** Matching rules of entities in the want parameter
![want-entities](figures/want-entities.png)


### Matching Rules of uri and type in the want Parameter

When the **uri** and **type** parameters are specified in the **want** parameter to initiate an application component startup request, the system traverses the list of installed components and matches the **uris** array under **skills** of the application components one by one. If one of the **uris** arrays under **skills** matches the **uri** and **type** in the passed **want**, the matching is successful.

There are four combinations of **uri** and **type** settings. The matching rules are as follows:

- Neither **uri** or **type** is specified in the **want** parameter.
  - If the **uris** array under **skills** of an application component is unspecified, the matching is successful.
  - If the **uris** array under **skills** of an application component contains an URI element whose **scheme** and **type** are unspecified, the matching is successful.
  - In other cases, the matching fails.

- Only **uri** is specified in the **want** parameter.
  - If the **uris** array under **skills** of an application component is unspecified, the matching fails.
  - If the **uris** array under **skills** of an application component contains an element whose [uri is matched](#matching-rules-of-uri) and **type** is unspecified, the matching is successful. Otherwise, the matching fails.
  - If the matching fails for the preceding two scenarios and the input URI is a file path URI, the system obtains the MIME type of the file based on the file name extension. If the MIME type matches **type** configured under **skills**, the matching is successful.

- Only **type** is specified in the **want** parameter.
  - If the **uris** array under **skills** of an application component is unspecified, the matching fails.
  - If the **uris** array under **skills** of an application component contains an URI element whose **scheme** is unspecified and [type is matched](#matching-rules-of-type), the matching is successful. Otherwise, the matching fails.

- Both **uri** and **type** are specified in the **want** parameter, as shown below.
  - If the **uris** array under **skills** of an application component is unspecified, the matching fails.
  - If the **uris** array under **skills** of an application component contains an element whose [uri is matched](#matching-rules-of-uri) and [type is matched](#matching-rules-of-type), the matching is successful. Otherwise, the matching fails.

Leftmost URI matching: When only **scheme**, a combination of **scheme** and **host**, or a combination of **scheme**, **host**, and **port** is configured in the **uris** array under **skills** of the application component, the matching is successful only if the leftmost URI in the passed **want** parameter matches **scheme**, the combination of **scheme** and **host**, or the combination of **scheme**, **host**, and **port**.

**Figure 3** Matching rules when uri and type are specified in the want parameter
![want-uri-type1](figures/want-uri-type1.png)

To simplify the description:

- **uri** in the **want** parameter passed in by the caller is called **w_uri**; each element in the **uris** array under **skills** of the application component to match is called **s_uri**.
- **type** in the **want** parameter passed in by the caller is called **w_type**; the type in the **uris** array under **skills** of the application component to match is called **s_type**.

**Figure 4** Matching rules of uri and type in the want parameter
![want-uri-type2](figures/want-uri-type2.png)


### Matching Rules of uri

The rules are as follows:

- If **scheme** of **s_uri** is unspecified and **w_uri** is unspecified, the matching is successful. Otherwise, the matching fails.

- If **host** of **s_uri** is unspecified and **scheme** of **w_uri** and **scheme** of **s_uri** are the same, the matching is successful. Otherwise, the matching fails.

- If **port** of **s_uri** is unspecified and the combination of **scheme** and **host** of **w_uri** is the same as the combination of **scheme** and **host** of **s_uri**, the matching is successful. Otherwise, the matching fails.

- If **path**, **pathStartWith**, and **pathRegex** of **s_uri** are unspecified and the combination of **scheme**, **host**, and **port** of **w_uri** is the same as the combination of **scheme**, **host**, and **port** of **s_uri**, the matching is successful. Otherwise, the matching fails.

- If **path** of **s_uri** is specified and the **full path expressions** of **w_uri** and **s_uri** are the same, the matching is successful. Otherwise, the matching of **pathStartWith** continues.

- If **pathStartWith** of **s_uri** is specified and **w_uri** contains the prefix expression of **s_uri**, the matching is successful. Otherwise, **pathRegex** matching continues.

- If **pathRegex** of **s_uri** is specified and **w_uri** meets the regular expression of **s_uri**, the matching is successful. Otherwise, the matching fails.

> **NOTE**
>
> The **scheme**, **host**, **port**, **path**, **pathStartWith**, and **pathRegex** attributes of **uris** under **skills** of an application component are concatenated. If **path**, **pathStartWith**, and **pathRegex** are declared in sequence, **uris** can be concatenated into the following expressions:
>
> - **Prefix URI expression**: When only **scheme**, a combination of **scheme** and **host**, or a combination of **scheme**, **host**, and **port** is configured in the configuration file, the matching is successful if a URI prefixed with the configuration file is passed in.
>     * `scheme://`
>     * `scheme://host`
>     * `scheme://host:port`
> - **Full path expression**: `scheme://host:port/path`
> - **Prefix expression**: `scheme://host:port/pathStartWith`
> - **Regular expression**: `scheme://host:port/pathRegex`


### Matching Rules of type

> **NOTE**
>
> The matching rules of **type** described in this section are based on the fact that **type** in the **want** parameter is specified. If **type** is unspecified, follow the [matching rules of uri and type in the want parameter](#matching-rules-of-uri-and-type-in-the-want-parameter).

The matching rules are as follows:

- If **s_type** is unspecified, the matching fails.

- If **s_type** or **w_type** contains the wildcard `*/*`, the matching is successful.

- If the last character of **s_type** is the wildcard `*`, for example, `prefixType/*`, the matching is successful only when **w_type** contains `prefixType/`.

- If the last character of **w_type** is the wildcard `*`, for example, `prefixType/*`, the matching is successful only when **s_type** contains `prefixType/`.