Requirements Modelling and Specification for Service Oriented Architecture

5.2. Conversations

A business process is thus a network of commitments represented by conversations and contracts.

Figure 5.1. A conversation.

A typical conversation is represented as (part of) a rich picture in Figure 5-1 where a typical external customer agent places an order with some business. This message includes the definition of the reply: {order accepted|out of stock|etc.}. We have, quite legitimately I think, used the UML use case symbol to represent the conversation, but stereotyped the UML classifier symbols to represent customer and business unit agents.

A message implies that data flow, so that this approach generalizes the more dataflow-based modelling techniques of Chapter 4. However, it also enriches them considerably. For one thing, data flow in both directions along message links (via the request and hand-over stages discussed below). This is why we have chosen to terminate message links at the recipient end with a filled circle rather than an arrowhead. The line segment is directed from the initiator (when known) of the communication, not from the origin of the data.

We now begin to see that agents can be modelled as objects that pass messages to each other. Clearly agents can also be classified into different types as well. UML actors are a specialization of our agents.

A semiotic or speech act is characterized at the semantic and pragmatic levels by a (possibly ...