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236 Ch. 12 Service-Oriented Logical Design Relationship
Apparent Unidirectional Relationship
Implied Bidirectional Relationship
Apparent Bidirectional Relationship
Comment
Implied Unidirectional Relationship
EXHIBIT 12.1 SERVICE-ORIENTED LOGICAL DESIGN
RELATIONSHIP CONNECTORS
There are two categories of service relationship connectors.
1. Apparent relationship. This denotes a visible association between two services or
between a service and its consumer. The term ???apparent??? describes a message path that
directly links entities, with the carried information being passed to and from communicating
parties without making use of brokers or intermediary services.
2. Implied relationship. This icon group illustrates an invisible service relationship. The
hidden relationship pertains to indirect associations that employ brokers for message
delivery. Thus, an implied service relationship is formed when intermediaries, service
proxies, or service hubs are located between consumers and services or between services
and their peers.
As may be apparent, the direction of message passing is also an important aspect of this
notation. There are two types of message routing directions to be aware of:
1. Unidirectional relationship. A unidirectional service relationship identifies a one-way
message path??”that is, messages are being delivered in one direction. No reply is necessary:
This is known as the fire-and-forget model.
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