Distributed Computing Applications and Infrastructure (IS 206)
Fall 1998
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Communication Services

Overview

Global Web Developer is reliant on numerous communication services to enable its various components to do their jobs. In addition to use for communication between components, these specialized communication services are requisite to support several of GWD's features, notably the Real Time Collaboration environment. GWD also makes extensive use of email services for communicating "events" to both application and website users. The nature and role of communication services in GWD are detailed below.

Useful Communication Services

The following table lists the four communication services used by GWD. For each communication service, a brief summary of the valuable role that service plays for GWD is provided.

Communication Service Application Uses
Message This service is used by GWD for communication between modules, either for a given module to direct or to inform another module(s).
Message with multiplexing
and queueing		 This type of service is employed many times in GWD. All email sent to users takes advantage of this service's properties. Multiplexing and queueing is also required for countless internal application communications such as retrieval or saving of system documents.
Message with reply This is another fundamental service extensively used by GWD, most obviously whenever a user requests a webpage. This service's use is frequent due to GWD's client-server architecture and especially the use of a network browser for the interface. This service also sees heavy use in internal application functions as well.
Conversation A conversation type of communication service is most notably used for the Real Time Collaboration environment of GWD. A shared context session is also used by some application-level functions such as simply authorizing users.

Elaboration on Communication in GWD

In conjunction with the different technical types of communication service covered above, GWD makes use of specialized types of communication which have very specific properties. An example already mentioned is email (direct, deferred), which is realized by implementing a special messaging system with multiplexing and queueing. Other fairly standard types of human communication supported by GWD's Real Time Collaboration environment are video and sound (both direct, immediate). These are both realized by the implementation of a conversation, or shared context session. Taken together with the collaborative editing, these collaboration support features compose a remote conferencing system with shared workspace. These examples illustrate how the four basic types of communication service listed above can be exploited not just for module to module communication internal to the application, but also for facilitating meaningful human communication. Because even GWD's most elaborate communication function, the collaboration environment, can be realized with the communication services covered by the text, no new services need to be defined for this particular application.

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last updated 11/24/98