Riel, Chapter 9

Discussion Questions submitted for Chapter 9 of Riel

Logical and Physical Object-Oriented Design

1. I don't understand why object oriented designers shouldn't allow physical design criteria to corrupt their logical designs. It seems that following physical design is more cost effective in the real world. If the logical design is corrupted and a new, correct logical design is created, I don't see the need of Heuristic 9.1. - Elias Vafiadis
2. At what stage in the development process should logical design be considered?
3. Shouldn't you keep the physical design criteria in mind when doing their logical design, so it is sure that the logical design can be implemented? -Jim Finnessy
4. Can you clarify the differences between logical and physical object oriented design? Why do they differ?(Sam Vanderhyden)
5. Could we please discuss the proper transition from physical design to logical design? ~yasir.

Wrappers

6. Could you explain wrappers more especially in the context of our project. taha
7. Can you expand upon the definition of a wrapper? Patrick Dowd
8. What is a wrapper? (Sam Vanderhyden)
9. It is now clear to me when it is necessary to have a wrapper, but not how to make wrappers. Could you explain it? --Hisako
10. Can you explain how one can use wrapping to ensure that heuristc 9.1 is effective? Anthony Fynn
11. How much work is actually involved in wrappers? How much effort would it have taken to use the database for our project?

Shallow and Deep Copies

Definitions

• Shallow Copies: Variables or fields are pointers that refer to a single, common object.
• Deep Copies: Variables or fields specify distinct copies of objects.

12. Can you clarify the idea behind using flags to mark shallow copies? --Khong
13. How do we implement deep and shallow copying in Java? Steve F.

Active and Passive Objects

Definitions

• Active Objects: In concurrent object-oriented programming, instances with built-in mechanisms for concurrency.
• Passive Objects are one of two types:
  • Concurrency has not been considered, and parallel threads may yield invalid results or illegal object states.
  • Concurrency issues have been resolved through explicit implementation of blocking mechanisms.

14. Can you go over the difference between passive and active objects more? -Kensler
15. What are passive objects?
16. Could you clarify concurrent object programming?
17. Could you explain the ATM scenario a little more. -George

Memory Management Issues

18. What set of circumstances would require a programmer to use reference counting? Patrick Dowd
19. Can you clarify reference counting?
20. How do we resolve the issues between garbage-collecting and nongarbage-collecting languages concerning memory management? --Khong
21. Does one need destructors for most code that one writes and do we need a destructor in the scheduler project? taha
22. Are deconstructors necessary or even possible in Java? - Jim Finnessy
23. What are the benefits of a destructor in coding? Anthony Fynn
24. I didn't understand the discussion of garbage collection too well. Could you explain it in simpler terms? --Ben Kaiser

Object-Orientation with Non-OO Languages

25. In 9.8, how to implement O-O design in nonobject-oriented languages, but do people actually still try to do this? what is the advantage of programming O-O design in nonobject-oriented languages, if people still do? --Hisako
26. Are there any advantages in the present to use object-oriented design in non-OO languages? Steve F

Other Questions

27. Could you describe CORBA architecture? Dessislava Dimova
28. What is the difference between object and record? (Raz Magar)
29. How might "persistence in space" be implemented? This sounds like a useful idea... Todd
30. Can one safely apply an object-oriented attitude toward all real world problems, or are there some limitations? -George
31. What are routing algorithms, how are they centralized, and why could decentralization make them simpler? Dessislava Dimova
32. Section 9.5 suggest we create a minimal public interface for all classes that are going to be reused. Is that for a physical or a logical design? - Elias Vafiadis
33. Could you explain the implementation of polymorphism in nonobject-oriented languages? (Raz Magar)
34. Can you tell me more about persistence in space (i.e. where it is currently being used, what's currently being developed in the area, etc)? -Kenslerj
35. Could you speak a little more about object oriented databases... Todd
36. Could we please discuss heuristic 9.2 with an example from our project? ~yasir.

This document is available on the World Wide Web as

http://www.cs.grinnell.edu/~walker/courses/223.sp02/read-riel-9.html

created April 26, 2002 last revised May 6, 2002
For more information, please contact Henry M. Walker at walker@cs.grinnell.edu.