FIT 2001 Week 8

 Lecture 

Its been awhile since I kept up with blogging on FIT 2001... I was swamped that week with loads of assignments. Its just crazy when suddenly in that one week you have more then 4 assignments due...

Anyway on to the business at hand...

Design Use Case Realization...Wow this topic had a huge bunch of information to take in, for a two hour lecture...

The 4 symbols for entity, control , boundary and data access can be used in a Robustness diagram which shows the initial system design.

• Entity – Seems like domains of the problem to me
• Boundary – System wall boundary between user and system
• Control – between view layer and domain layer there is this message flow that needs to be manage and the control does that
• Data access –Accessing data

The above is what I took from the lecture on it....The lectures provide a more formal definition but I needed something more intuitive.

Coupling is the measure of how the classes are linked.

Cohesion is the measure of consistency of functions in a single class.


Coupling and cohesion are very important. Its best to have low coupling so most classes are independent...It is reducing dependencies. Also good practice to have classes of high cohesion then a single low cohesion class.

Examples that I would use would be a car has many coupled parts like driveshaft and gearbox but it has high cohesion means that the gear box does it's function to switch gears and the driveshaft is just to transmit power to a differential and then to the wheels. If dependencies could be reduced then the car would run even more efficiently and maintenance will be easier. Less moving parts.

Same for an information system.You want to reduce as many dependencies as possible.

To get to the Package diagram which shows the 3 different view of objects. The robustness diagram is used to develop the first cut sequence diagram, and then the more complete sequence diagram using the additional view layer and data access objects are added on and then the final class diagram inclusive of methods and visiblity will lead to the package diagram.

Tute

Took me a long time to understand what was going on regarding the work involve. But once the robustness diagram is figured out, it is so much simpler to progress towards the package diagram.

I found that the Use Case Narrative can be described as an Activity Diagram. I only just started reading the SJB text book and I find that I should continue if its not too late to start reading it in detail because concepts like this aren't obvious to me.

Also the solutions are for review questions on page 430 but the questions are for page 474...Very interesting.....