The universe of objects in Flex can be divided into a set of inherently private and shared objects. An object may contain any number of references to other objects. The shared objects can be either passive or active. Active objects are associated with a dedicated process usually known as an object server. Active objects are usually large grained and are not cached in our system. Passive objects do not have a process dedicated to them and can be cached.
The system architecture of Flex is defined by the caching framework shown in figure 2 which consists of the important classes that enable caching. As shown in the figure, the framework consists of three subtrees. The left-most subtree shows the various styles of accessing distributed objects and this is the framework that is visible to the users. These classes are distinguished with double lines in the figure. Class implementors subclass from one of these classes directly or indirectly while invoking distributed objects. These classes constitute what we call the consistency framework. The remaining branches define the classes which are transparent to the application programmers. These define the code that is executed by the various cacher processes discussed in the previous section. These classes define what we call the implementation framework.
