Physical Model Design Considerations

The physical model defines the ways in which packages are produced and consumed. This model is based on three components: a producer, a consumer, and a pipe between them.

Figure: G–1. Components of the physical model

A producer is a piece of software or a device that writes packages. A consumer is a piece of software or a device that reads packages. A device is a piece of hardware, such as a printer or scanner that performs a single function or set of functions. Data is carried from the producer to the consumer by a pipe.

In local access, the pipe carries data directly from a producer to a consumer on a single device.

In networked access the consumer and the producer communicate with each other over a protocol. The significant communication characteristics of this pipe are speed and request latency. For example, this communication might occur across a process boundary or between a server and a desktop computer.

In order to maximize performance, designers of physical package formats consider access style, layout style, and communication style.