The component types identified in our design are as follows:
1. User interface (UI) components. Most solutions need to provide a way for users
to interact with the application. User interfaces are implemented using Microsoft ASP.NET pages, controls, or any other technology you use to render and format data for users and to acquire and validate data coming in from them.
2. User process components. A user interaction with the system follows a predictable process. To help synchronize and orchestrate these user interactions, it can be useful to drive the process using separate user process components. This way the process flow and state management logic is not hard-coded in the user interface elements themselves,and the same basic user interaction “engine” can be reused by multiple user interfaces.
3. Business workflows. After the required data is collected by a user process, the data can be used to perform a business process.
4. Business components. Regardless of whether a business process consists of a single step or an orchestrated workflow, your application will probably require components that implement business rules and perform business tasks.
5. Service agents. When a business component needs to use functionality provided in an external service, you may need to provide some code to manage the semantics of communicating with that particular service.
6. Service interfaces. To expose business logic as a service, you must create service interfaces that support the communication contracts (message-based communication, formats, protocols, security, exceptions, and so on) its different consumers require. For example, the credit card authorization service must expose a service
interface that describes the functionality offered by the service and the required communication semantics for calling it. Service interfaces are sometimes referred to as business facades.
7. Data access logic components. Most applications and services will need to access a data store at some point during a business process.
8. Business entity components. Most applications require data to be passed between components. The data is used to represent real-world business entities, such as products or orders. The business entities that are used internally in the application are usually data structures,such as DataSets, DataReaders, or Extensible Markup Language (XML) streams,but they can also be implemented using custom object-oriented classes that
represent the real-world entities your application has to work with.
9. Components for security, operational management, and communication. Your application will probably also use components to perform exception management, to authorize users to perform certain tasks, and to communicate with other services and applications.