Guideline: Identify Service Interfaces from Collaboration Role Interaction Patterns presents four rules for describing ServiceInterfaces based upon pairs of interacting roles in Service
Collaborations. The rule illustrated here is:
Rule 2: Define the ServiceInterface and its provided and required interfaces from the perspective of the role
that is messaged first. The role in the interacting pair that sends the first message is the
consumer; the role that receives the first message is the provider. Always define ServiceInterfaces
from the provider's perspective.
The following figure shows "role1" messaging a "role2." role1 is the consumer, and role2 is the provider. Describe the
ServiceInterface and any interfaces that are involved in this interaction from the perspective of role2.
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