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Overview

There are two main, tightly-coupled concepts in DADL which are the conversation and the participants. The conversation has an identity independent of the participants. Contracts govern the behavior of the conversation and the expectations of the participants. A conversation is of little use without participants. Likewise, participants are of little use without communication taking place in a conversation.

The participants produce and consume the conversation. These participants are distributed agents, or simply dagents.

Dagents communicate with other dagents to accomplish tasks. A dagent may be involved in many conversations, potentially entering and leaving a conversation at times. The identity of the dagent at the other end of the conversation may be unknown.

For each conversation, a domain-specific language is defined. The base level unit of a communication is a term. Terms are built from characters taken from an alphabet. Multiple terms from the same dagent form a sentence while multiple sentences between dagents form a conversation. The conversation uses one alphabet.

The conversation is carried over a bi-directional connection. Information can be placed on a connection from many sources. The dagents may be unaware of the origin of the information. What happens to the information after it is placed on the connection is governed by the conversation manager.

The connection may be multi-sided in which case many dagents may get involved in the conversation.

A dagent may provide value by performing some service, or function, while the conversation is taking place and contributing the results back to the conversation.

The dagents agree to a contract to determine their behavior and expected behavior of all other agents participating in the conversation. A dagent may provide many services to the conversation.

Both the conversation and the dagents exist in an environment. From the environment, resources are provided and consumed.

The services that a dagent provides, the underlying definition of the conversation, along with the contract collectively define the architecture within an environment.


next up previous contents
Next: Backus-Naur Form (BNF) Semantics Up: Distributed Architecture Description Language Previous: Distributed Architecture Description Language
Ronald LeRoi Burback
1998-12-16