Guidelines: Business Use-Case Realization
Topics
A business use-case model describes a business in terms of business actors
and business use cases corresponding to customers and business processes. The
business use-case model includes workflow descriptions that identify what
is done. How the work is performed in each business use case is
described in the business analysis model.
A set of individuals who perform the work of a business use case,
together with the business objects they access and manipulate as part of the
job, is called the business use-case realization. Objects of the same class can
participate in several different business use-case realizations, reflecting that
the same kind of resource from one time to another works in different processes.
The first choice to document the realization of a business use case is to
draw an activity diagram, where swimlanes (or partitions) represent the
participating business workers. For each business use-case realization, there
may be one or more activity diagrams to illustrate the workflow. A common way to
organize is to have one overview diagram without swimlanes that cover the whole
workflow, and where you show "macro activity" that are at a high
level. Then, for each such macro activity there is a more detailed activity
diagram that shows the swimlanes and the activities at the business worker
level. For readability reasons, a goal should be that each diagram fit on a
page.
See also Guidelines: Activity Diagram in the
Business Analysis Model.
For each business use-case realization there can be one or more interaction
diagrams depicting its participating business workers and business entities, and
their interactions. There are two types of interaction diagrams: Sequence
diagrams and communication diagrams. They express similar information, but show
it in different ways:
- Sequence diagrams show and explicit sequence of events and are better than
activity diagrams for more complex scenarios.
- Communication diagrams show the communication links and messages between
objects and are better for understanding all of the effects on a given
object.
- If alternative flows are few, but there are many business entities
involved, interaction diagrams are often a better choice than the activity
diagram to show the realization of the workflow.
See Guidelines: Sequence Diagram in the Business
Analysis Model and Guidelines: Communication Diagram in
the Business Analysis Model for more information.
For each business use-case realization there may be one or more class
diagrams depicting its participating business workers and business entities. A
diagram of this kind can be a useful help when coordinating all the requirements
on a business worker or business entity that participates in several business
use-case realizations. See Guidelines: Class Diagram in
the Business Analysis Model.
Relationships between business use cases correspond to relationships in the
business analysis model. By studying what happens in the business, you can
understand how to map the business use-case relationships to links between
objects of the business use-case realizations. For more on use-case
relationships, see Guidelines: Business Use-Case Model.
Suppose a business use case (base) includes another business use case
(inclusion). At a given moment, the employees will need to cease following the
instructions of the base and switch to following the instructions of the
inclusion as described in the documentation of the respective business use-case
realizations. The following happens:
- An identifiable state is reached in the execution of a process according
to the base use case-a business worker has finished a certain task for example.
- A change in state is noticed by someone who is ready to start working
according to the realization of the inclusion. Either the person sees some
phenomenon, or is informed by someone in the inclusion.
A business worker in the realization of the base interacts with the business
workers in the realization of the inclusion to inform them of what is going on.
The most natural modeling approach is:
- A realization of the inclusion has one object for each base it is included
by. The objects originating from the base each have a link to the business
worker individual that starts the work in the inclusion.
Each business worker in the realization of the base
business use cases needs a link to the business worker that starts the work
according the inclusion business use case.
- A realization of the base business use case does not have objects
representing the inclusion.
In the case of a business use case being extended by an another business use
case, you will end up with a similar solution. In the realization of the
extension, you will have one object representing the base, that has a link to an
object initiating the work described within the extension.
Each business worker in the base business use cases needs
a link to the business worker that starts the extension.
For use-case-generalization, the solution is again similar. In the
realization of the parent use case, you will see an object representing the
child.
There are business workers representing the child use
cases in the realization of the parent.
The use-case relationships have different interpretations. When it comes to
their representations in the business analysis model, the difference is found in
why the work defined in the inclusion, the extension or the parent business use
case is initiated and how the business worker interprets the information. How the
objects in the business use-case realizations interact follow the same structure
in all cases.
- The participating business workers and business entities perform the
business use-case's workflow, including all alternative and optional
subflows.
- Workflow description covers all the activities described.
- The business workers and business entities have all the relationships
needed to perform the business use-case's workflow.
- At least one business worker handling the interaction between the business
actors and the business.
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