Discussion Questions for Riel, Chapters 1-2
Complexity
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Riel says that the object oriented approach avoid accidental
complexity. What elements of other programming paradigms cause them have
accidental complexity while object oriented programming does not?
(Jonathan)
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On Page 3, Riel describes how object oriented programming helps eliminate
accidental complexity. Does object orineted programming help eliminate
essential complexity. If so how? (Gaurav)
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If there is no "methodology or tool " to eliminate essential complexity,
how does one deal with it? (Saugar)
Prototyping
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The author says that same-language prototyping is the most common type. Is
this still the case, or has the UML popularized different-language
prototyping to the extent that it is now more common than same-language
prototyping. (Elijah)
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In same-language prototyping, is the idea to write feature-incomplete, but
compilable code, or is it simply used as a pseudo code? (Elijah)
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How does different-language prototyping prevent "accidentally" shipping
garbage code? (Alex)
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Why would a team ever want to use two different languages for creating
software? The drawback of garbage code, as Riel calls it, should only be an
issue if there isn't enough time to properly complete the software.
(Jonathan)
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Is there a good reason why a software company would use Different-Language
Prototyping? It seems counter intuitive to me to write the software in one
language for testing and then to re-write it in another language after
testing has been finished. Is there any advantage to using this method?
(Dave V.)
Language and Organizational Issues
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The author talks about "paradigm shift" (pg.2). Are there only two
paradigms in the software world,i.e "centralized control of structural
approach" and "decentralized fashion"? (Saugar)
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What are the advantages of a multiparadigm language? (David D.)
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Do we have destructor of the class in Java? (Sheng)
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Why has the level of software reuse in object-oriented applications been
disappointing for many developers? I thought that object oriented
programming languages had always relied on software reuse, so what sparked
the sudden excitement with reusing software? (Mike C.)
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What do you think about corporate hierachy of great designers? (David D.)
Principles for Class Design
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When Riel talked about god classes, I think he implied that they would
contain a whole lot of code. Now, I've read about in other places, and had
some success myself when using, classes called things like
'BlahBlahBlahSystem' that orchestrate the running of complex processes.
The thing is, the 'System' classes I've dealt with have all been fairly
small, with fairly concise public interfaces (Run(), Abort(), etc.). They
contain a few powerful components which interface with each other simply
and themselves contain a small set slightly less powerful and more specific
components. This trend continues down for several more levels of
granularity without ever resulting in an overly complex or bulky class. Is
the kind of 'System' class I'm talking about the same thing as Riel's god
class, or is it more permissible? (John)
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Heuristic 2.7 says that Classes should only exhibit nil or export coupling
with other classes, then in what cases would we use export, covert and
overt coupling? would using the other types of coupling affect Class
cohesion? (Gaurav)
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From Heuristics 2.8, how primitive should the one key abstraction each
class represent be? How do we judge that the abstraction is not too general
or too specific? What system can be used to keep track of classes
created?(other than javadoc) (Chayapan)
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I'm a little confused as to the meaning and use of and abstract class. Can
you provide an example, or at least a type of class that's considered
abstract?? (Dave V.)
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Do overt and covert couplings have any practical differences? Although by
Heuristic 2.7, both couplings are bad, is there a reason that you'd choose
one over the other? (Alex)
Data within Classes
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Can you please explain further what riel means by all data should be hidden
withing its class. (Monica)
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Are there any cases where data should be made public? (Mike L.)
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Riel keeps bringing up a 'Point' class when talking about separating data
from public interfaces. Now, I think I have at least a decent
understanding of why this is important for larger, or less well understood
classes, but it seems a little unwieldy for something like a point. PODs
don't have public interfaces; they're well understood and you access them
directly. It seems reasonable for the purpose of readability to have a
library of certain small, well understood classes (such as Points) that
expose their data and can be treated more-or-less like PODs. Would Riel
object to this? (John)
Class Methods
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The reading recommends minimizing the methods of a class, and that some
have made the opposite recommendations. Just how minimal is a "minimized"
class? Is there a happy medium between simplifying code and providing
useful operations? (Lorelei)
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"Minimize the number of messages in the protocol of a class." from the
textbook cannot convince me, would someone explain that principle to me
creatively? (Sheng)
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Please clarify dynamic semantics and how one would use local states in a
method. (Lorelei)
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What is a common-code private function? (Mike L.)
Additional Questions
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Can you explain how object-oriented databases work? (Chayapan)
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What does it mean for a class to instantiate objects? (Monica)
This document is available on the World Wide Web as
http://www.cs.grinnell.edu/~walker/courses/223.sp05/readings/riel-1-2.shtml
