Guideline: Identify the Structure of a Business Use-Case Realization
Use the sequence diagrams in a business use-case realization to define the structure of elements participating in that realization.
Relationships
Related Elements
Main Description

Each message between business elements on a sequence diagram must be supported by a structural relationship. For instance, a business worker can't request that a business entity perform an operation without having some way to inform the entity of the request. The nature of the relationship depends on what the element is, so the relationship could represent a network connection, an interpersonal relationship, a business contract, etc.

See Example: Class Diagram realizing a Business Use Case for an example of a business use-case realization structure.

Identify the Relationships in a Sequence Diagram

Create one UML class diagram for your business use-case realization. This diagram illustrates the structure required to support all relationships needed to realize the scenarios in the business use-case realization. Add all the business elements from all the sequence diagrams into the class diagram. There will likely be many business elements that appear in multiple sequence diagrams. These only need to be added to the class diagram once.

For each message or request that's made from one business element to another, add a one-way association in the class diagram from the requesting element to the element that performs the requested operation. If you find two elements that make requests of each other, use a single bi-directional association. If a relationship from one entity to another already exists, leave it alone (any number of operations can be requested using a single relationship)

Add Multiplicity and Roles

Examine the relationships and determine their multiplicity. Start with 1-to-1 relationships and ask if one element needs to access more than one instance of another element. For example, sequence diagrams can show that a service supports requests from various business elements of the same type. If it can handle those requests in parallel, there will be a many-to-one relationship between the elements.

Check Diagram for Readability and Consistency

Review the diagram to assure it's readable and properly describes the relationships between business elements. Make any changes necessary that will improve the accuracy and usability of the information.

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