Summary (Top)
See text Table 3.1 on page 106

Elements (Top)

• Components
  Components are runtime processors and data stores. Components are usually implemented with a combination of custom, reusable, and purchased modules (cots). The goal is to reduce the number of custom modules that must be developed to implement a component.

  Some examples of purchased and reusable modules are sorters, XSLT transformers, XML parsers, and database management systems.

• Connectors
  Connectors are mechanisms that allow for the exchange of data between components. Connectors are usually implemented using purchased modules (cots), technologies, and protocols. The format of the data that is exchanged may be custom or standard. The content of the data that is exchanged is often custom. The goal is to use purchased middleware and increase the use of standard formats.

  Two systems that must interact are really just large components with one or more connections. These connections are interfaces between the systems.

Example (Top)

Suppose that the practical requirements for the automated portion of an enterprise application are given by the following essential events:

Event: Client A Submits Transaction
Message Stimulus:	Receive transaction http web form from Client A.
Update Response:	Add transaction to database.
Message Response:	Send acknowledgement http web page to Client A.

Event: Client B Requests Activity Report
Message Stimulus:	Receive http request from Client B.
Message Response:	Send transaction summary http web page to Client B.
Message Response:	FTP transaction detail file to Client C.

Then Figure 1 shows a basic architecture for an application that meets these requirements. Because the events are asynchronous, a shared data style is used:

Figure 1: Event Driven Application Architecture

Discussion Questions:

1. What component-and-connector styles are used in this model?
2. Why does the model show an input data flow to the Event 1 Processor but not to the Event 2 Processor?