Question on class diagram

[Dhiren Joshi]

Hi Everyone,
I have seen in the posts that class diagrams have consisted of domain classes and sometimes sub systems. Ref: https://coderanch.com/t/138268/sr/certification/Passed-SCEA-Part-II-III
I am confused why class diagram doesnt consist of only domain classes.
How would representing as subsystem and domain classes be different/advantageous instead of using only domain classes.
Also how do u represent a subsystem in a domain class diagram.
Thanks
Dhiren

[Sridhar Raman]

Hi Dhiren,
Hope your part II prep is coming along well. I have given some explanations to your questions below.
>>>I am confused why class diagram doesnt consist of only domain classes.
UML is flexible and allows you to show elements that may not be usually used in certain diagrams. For class diagrams, the common approach is to show only classes and class associations. You could also show subsystems (packages) in a class diagram but subsystems are usually shown in the component diagram along with the interfaces.
>>>How would representing as subsystem and domain classes be different/advantageous instead of using only domain classes.
When you have many redundant/similar classes that can be easily represented as a single element in the UML model, you may opt for representing them as a package (or subsystem). For example, if you have a business area that is not directly related to the system you are dealing with, say Customer Service, you may want to show it as a package in your class diagram. In this case, you would show a dependency between the customer and the customer service package, instead of depicting more fine-grained relationships between customer and the classes in the customer service package.
>>> Also how do u represent a subsystem in a domain class diagram.
Package notation. Some tools may not support this feature.

Sridhar-

[Dhiren Joshi]

Thanks Sridhar ,
Very help ful suggestions .I checked rose and see the package notations so I am now adding that and cleaning up my class diagram which was looking ugly with all the lines crossing over.
On a similar line for component diagram when I represent the subsystem with package ,do I need to show components inside the package diagram.
I checked and rose does support that feature but I am not sure if that is the correct norm to use to depict the components embedded inside a packaged subsystems. Cade doesnt show components inside a subsystem in the component diagram.
Thanks for your help.
Dhiren

[Sridhar Raman]

Hi Dhiren,
>>> On a similar line for component diagram when I represent the subsystem with package ,do I need to show components inside the package diagram.
You could show the contents of the package along with their visibility information but most tools don't allow this. I usually attach a UML note to a package to explain what classes it contains and what the grouping(packaging) stands for.
>>> I checked and rose does support that feature but I am not sure if that is the correct norm to use to depict the components embedded inside a packaged subsystems.
Rose doesn't support this. It does let you drill down into the package upon double-clicking and (think) you can specify your components here. However, it won't be of much help from the exam's point of view and I would go with using UML notes and keep things simple.
Sridhar-

[Sridhar Raman]

FYI, Visio is quite flexible for using uncommon depictions in UML diagrams but it doesn't enfoce UML compliancy.
Sridhar-
[ April 21, 2004: Message edited by: Sridhar Raman ]

[Dhiren Joshi]

Hi Sridhar,
Thanks for all the prompt replies. I tried implementing some subsystems when I realised that my concepts in implementing them are not quite clear.
Can you give me some links pointers as to how to identify subsystems.
I was assuming from the all the posts that I read it would be a cake walk but when I tried implementing it I found it isnt so. There are many variables which I hadnt thought of so I have started adding some subsystems which look correct but for others I am not convinced.
Thanks
Dhiren

[Sridhar Raman]

Hi Dhiren,
The exam deals with the travel reservation business area. Look for other business areas that the travel reservation deals with and are involved in some interactions. They would be your subsystems. If there are a bunch of operations or business procedures for which you don't have much information about, and that related to or part of the travel reservation domain, they would also be good candidates for subsystems. These suggestion apply for components.
As for class diagrams, I normally avoid mixing packages with the classes in them.

Sridhar-
[ April 23, 2004: Message edited by: Sridhar Raman ]