"Use Case diagrams are used to model user/system interactions. They define behavior, requirements and constraints in the form of scripts or scenarios."
Ah, the joys of the english language.
Alternative parsings:
Use Case diagrams are used to model user/system interactions.
[subject] - [transitive verb]- [object] as in "Buckets are used to carry water." or "Cars are used to carry passengers."
They define behavior, requirements and constraints in the form of scripts or scenarios.
[subject] They
[transitive verb] define
[object] behavior, requirements and constraints.
[qualifier]in the form of scripts or scenarios.
is also...
They define behaviour in the form of scripts.
They define behavior in the form of scenarios.
but not ...
They define behaviour in the form of scripts and scenarios.
i.e. the phrase "scripts or scenarios" can be (should be) read like "cars or automobiles" as in
Cars (or if you are a citizen of the USA - "automobiles") carry people.
IOW, "The EA 'scenarios' tab of the use case properties form can be used to describe the interactions that occur between the user and the system pertaining to the use case as a 'script'." Where script is to be taken in the theatrical sense rather than the technological sense, i.e.
System: Displays log in prompt.
User: Enters log in ID, e.g. "root" and presses return key.
System: Displays password prompt.
User: Enters log in password, e.g."******" and presses return key.
System: Validates ID and password pair and if OK grants access to the vt.
hth
Bruce
