The architecture of XXX Sample Clauses

The architecture of XXX. In [11], the authors propose an object-oriented architecture based on the event channel ab- straction and denote it by XXX. A distributed application constructed on top of EVA is de- fined as a set of cooperating objects, called components, that communicate mainly by exchang- ing special objects, called events, via an event channel and also by invoking special operations, called services. The interaction between components is either asynchronous (by the means of events) or synchronous (by the means of services). An entity in EVA may act as both a producer and a consumer of events and may be subordinated to any number of components. Any entity is first required to register or subor- dinate itself to a corresponding component before it can consume and produce events. The component is in charge of managing an event channel that has the role of routing the events produced by a subordinated producer to all interested subordinated consumers. The event channel decouples suppliers from consumers yielding the sought flexibility. Components provide an interface that allows the subordinated entities to register/access the services they wish to offer/use to/from other entities that share the same component. A component can register the services defined inside it, to a super-component to which it is subordinated. This allows the access to the component’s services for external entities that share the same super- component. Components have two main roles: i) they control the interactions between sub- ordinated entities and ii) they provide a way of structuring applications into related entities, while hiding them from unrelated entities and yielding application design more modular. Figure 5.1 depicts the architecture of a super-component (Component E) composed of two sub-components (Component C and Component D), an entity (Entity X) and an event channel. Figure 5.1: Event Channel in EVA. In summary, the event-based architecture relies on the following four main concepts: i) events; ii) entities; iii) components; and iv) services. An event is a “container” object used to convey data from supplier to consumer entities, while a service allow synchronous com- munication. An entity is a “worker” object that interacts with other entities to implement part of the functionality of the application. A component is both a “structuring” object that assembles related entities together, as well as a “manager” object that coordinates the inter- actions of its subordinated entities. A c...