Exhibit 13.4
illustrates the four different beams that correspond to the design composition styles: circular beam,
hierarchical beam, network beam, and star beam.
Take a look at Exhibit 13.5 for an example. A payroll service must be somehow linked
to an accounts payable service. The payroll service would request release of funds to issue an
employee paycheck. The response from the accounts payable service would then indicate whether
the funds are available and would make the necessary updates to a company??™s balance sheet.
Thus, the beam that supports these two service structures denotes that these services exchange
Employee
Payroll Atomic
Service
Network
Bidirectional
Beam
Accounts
Payable
Composite
Service
EXHIBIT 13.5 PAYROLL NETWORK SUPPORTED BY BIDIRECTIONAL NETWORK BEAM
262 Ch. 13 Service-Oriented Logical Design Composition
Apparent Unidirectional Network Beam
Apparent Bidirectional Network Beam
Implied Unidirectional Network Beam
Implied Bidirectional Network Beam
EXHIBIT 13.6 NETWORK STRUCTURE BEAM ICONS
bidirectional messages and indicates that they are part of a larger construction form??”a network
pattern. Note that network beam is presented by a small triangle symbol on the beam itself.
Beams are employed to provide support for the design composition structure, denote the
logical relationship between service structures, and enable message flow between consumers
and services.
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