Usecase description system scope and sequence diagram

[Harry Chuks]

Hi Guys,

I quite new in architecting and I have not come across this kind of scenario, am just confused. Any help with my questions below will be most appreciated.

1. When describing a usecase, most the scope of operation be within the system you are designing(SUD) or can it be anything. For instance, can it include a high level operation of an external system that interacts with the SUD. My thought is that, since your design in for the SUD, the operations of the external system is out of scope, effectively a black box with a public API. Or can you treat an external system as a white box too.
2. For the sequence diagram, can we draw a system sequence diagram when describing interactions of an external system or must it be a sequence diagram.


I hope my questions are clear enough, thanks for any assistance.

[K. Tsang]

Welcome to the Ranch.

Henry Chigere wrote:
1. When describing a usecase, most the scope of operation be within the system you are designing(SUD) or can it be anything. For instance, can it include a high level operation of an external system that interacts with the SUD. My thought is that, since your design in for the SUD, the operations of the external system is out of scope, effectively a black box with a public API. Or can you treat an external system as a white box too.

The scope will be within the assignment (SUD). The external systems can be treated as a black box with a known API, which is meaningful such as a function/API call checkAvailableInventory. Such function's return type is most likely boolean and its input parameter is an Inventory object to check. Other return type and input parms can bu used of course.

These external system API can be assumed

The level of detail for the sequence diagram is operation/method level as you go from presentation to business to integration/persistence tiers.

Henry Chigere wrote:
2. For the sequence diagram, can we draw a system sequence diagram when describing interactions of an external system or must it be a sequence diagram.

What's a "system sequence diagram" and how it's different from a normal sequence diagram?

When communicating with an external system, you will usually be calling web service API for that system

SUD your system -- checkAvailableInventory --> external system

<-- return true/false --

[Harry Chuks]

Thanks Tsang for the quick response. I was just confused with the way the usecase was described, it kind of looks like they where describing what the external system does in other to satisfy the usecase in question. That is why I was concerned about scope of the usecase. Thanks again.

[Harry Chuks]

thanks