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Fig. 10.4 Resource Service external architecture

10.4.1 External Architecture

Figure 10.4 shows the service’s external architecture, and reveals no less than six
separate interfaces that it uses and/or provides to the external environment. The
service communicates with the engine via three interfaces:

Interface A is used to check the service’s connection to the Engine, to upload and
unload specifications (via the Case Management form), and to add and remove
custom services (via the Service Management form).
Interface B is where the bulk of the communication between the Engine and
Resource Service takes place. It is primarily used to handle work item and case
events (enablings, cancelations, timer expiries, and so on); to launch and cancel
cases, and maintain a running cases list; to checkout and check-in work items;
to suspend, unsuspend, and skip work items; to create new work item instances
(for dynamic multiple instance tasks); and to retrieve data schemas and other
metadata for tasks and specifications.
Interface E is used to query the Engine’s process logs when formulating an
allocation strategy reliant on historical data (e.g., the Round–Robin strategies).