1# Ability Framework Overview 2 3An ability is the abstraction of a functionality that an application can provide. It is the minimum unit for the system to schedule applications. An application can contain one or more `Ability` instances. 4 5The ability framework model has two forms: 6 7- FA model, which applies to application development using API version 8 and earlier versions. In the FA model, there is Feature Ability (FA) and Particle Ability (PA). The FA supports Page abilities, and the PA supports Service, Data, and Form abilities. 8- Stage model, which is introduced since API version 9. In the stage model, there is `Ability` and `ExtensionAbility`. `ExtensionAbility` is further extended to `ServiceExtensionAbility`, `FormExtensionAbility`, `DataShareExtensionAbility`, and more. 9 10The stage model is designed to make it easier to develop complex applications in the distributed environment. The table below lists the design differences between the two models. 11 12| Item | FA Model | Stage Model | 13| -------------- | ------------------------------------------------------------ | -------------------------------------------------------- | 14| Development mode | Web-like APIs are provided. The UI development is the same as that of the stage model. | Object-oriented development mode is provided. The UI development is the same as that of the FA model. | 15| Engine instance | Each ability in a process exclusively uses a JS VM engine instance. | Multiple abilities in a process share one JS VM engine instance. | 16| Intra-process object sharing| Not supported. | Supported. | 17| Bundle description file | The `config.json` file is used to describe the HAP and component information. Each component must use a fixed file name.| The `module.json5` file is used to describe the HAP and component information. The entry file name can be specified.| 18| Component | Four types of components are provided: Page ability (used for UI page display), Service ability (used to provide services), Data ability (used for data sharing), and Form ability (used to provide widgets).| Two types of components are provided: Ability (used for UI page display) and Extension (scenario-based service extension). | 19 20In addition, the following differences exist in the development process: 21 22* Different ability types 23 24  25 26* Different ability lifecycles 27 28  29 30For details about the two models, see [FA Model Overview](fa-brief.md) and [Stage Model Overview](stage-brief.md). 31
