MICROSOFT's COM+ [Obe00] promotes a model similar to the abandoned typed model of the CORBA EVENT SERVICE. Asynchronous invocations are viewed as events, but latter ones are not reified. The primary filtering is thus made on the types of the subscribers, as illustrated by Figure 2. By viewing an invocation as an event, the invocation arguments can be viewed as the attributes of the resulting notification. Filters in COM+ are expressed on invocation arguments through a limited subscription grammar. Encapsulation seems to be preserved by avoiding the reification of events.
| Subscriber s |
public class Chatter {
public void in(String from, ...); ... } |
| Criteria | ``message sent by Tom'' |
| Argument | String criteria = "from is Tom"; |
| Evaluation | from.equals("Tom") |