Lakhasly

rchitectural patterns, which I introduced in Chapter 6, are abstract, stylized descriptions of good design practice.As you might expect, the differences between embedded and interactive software means that different architectural patterns are used for embedded systems, rather than the architectural patterns discussed in Chapter 6.In this section, I discuss three real-time architectural patterns that are commonly used: 1.Observe and React This pattern is used when a set of sensors are routinely monitored and displayed.In response to environmental changes detected by the sensor, control signals are sent to the system actuators.The transformation is implemented as a sequence of processing steps, which may be carried out concurrently.This allows for very fast data processing, because a separate core or processor can execute each transformation.2.3.

rchitectural patterns, which I introduced in Chapter 6, are abstract, stylized descriptions of good design practice. They encapsulate knowledge about the organization of
system architectures, when these architectures should be used and their advantages
and disadvantages. You should not, however, think of an architectural pattern as a
generic design to be instantiated. Rather, you use the pattern to understand an architecture and as starting point for creating your own specific architectural design.
As you might expect, the differences between embedded and interactive software
means that different architectural patterns are used for embedded systems, rather
than the architectural patterns discussed in Chapter 6. Embedded systems’ patterns
are process-oriented rather than object- or component-oriented. In this section, I discuss three real-time architectural patterns that are commonly used:

1. Observe and React This pattern is used when a set of sensors are routinely monitored and displayed. When the sensors show that some event has occurred (e.g.,
   an incoming call on a cell phone), the system reacts by initiating a process to
   handle that event.


2. Environmental Control This pattern is used when a system includes sensors,
   which provide information about the environment and actuators that can change
   the environment. In response to environmental changes detected by the sensor,
   control signals are sent to the system actuators.


3. Process Pipeline This pattern is used when data has to be transformed from one
   representation to another before it can be processed. The transformation is
   implemented as a sequence of processing steps, which may be carried out concurrently. This allows for very fast data processing, because a separate core or
   processor can execute each transformation.
   These patterns can of course be combined and you will often see more than
   one of them in a single system. For example, when the Environmental Control
   pattern is used, it is very common for the actuators to be monitored using the
   Observe and React pattern. In the event of an actuator failure, the system may