This formation makes it
easier to rationalize, design, architect, and construct the business or technological relationships
that are maintained. But how can transaction activities be conveyed in such a chain of command?
The typical message flow in hierarchical formations is top-down or bottom-up. Top-down
service interaction means that a coarse-grained entity??”the parent service??”is also the one that
originates messages. Conversely, the bottom-up message propagation workflow begins with a
fine-grained service??”at the child level??”and moves up to engage a more general service. But
the service interaction and collaboration scheme can even devise message exchange on the same
hierarchical level??”between siblings. This scenario also should be considered when planning
service-oriented transactions.
Exhibit 14.20 exemplifies a hierarchical logical design composition diagram that will be
developed into a service-oriented transaction diagram. Note the unidirectional logical composition
beams that support this structure. The messages rise from the bottom to the top of the hierarchy.
In this scenario, the account balances atomic service is the one that is being updated with account
information by its two subordinate services: (1) The credit-card balances atomic service and its
child gold card balances atomic service. (2) The investment account balances atomic service and
its subordinate equity investment account balances atomic service.
Pages:
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522