Re: Agile Ecosystems Vs (Rational) Unified Process

From: Universe (universe_at_tAkEuniverceOuT.net)
Date: 08/19/04 

Date: Wed, 18 Aug 2004 23:01:24 -0400

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From: Universe (universe@radixundo.net)
Subject: Re: NewBie : What is Liskov's Principle of Substitution ?
View: Complete Thread (95 articles)
Original Format
Newsgroups: comp.object
Date: 2003-05-13 05:27:44 PST

S Perryman wrote:

> "Stefan Ram" <ram@zedat.fu-berlin.de> wrote in message
> news:b9qgeq$ltflm$1@fu-berlin.de...
>> "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de> writes:
>> > Because nobody needs a language
>> >where Square and Rectangle should be unrelated types as they are according
>> >to LSP.
>> "Square" and "Rectangle" are not types. These are
>> are just two words. Unless you specify what types these
>> words are supposed to label by listing the operations
>> supported by instances of these two types and by specifying
>> the meaning of these operations, no types are given.
>> Only after such a specification is given, one can start
>> to argue about their relation and apply the LSP.
> Here are some "specifications" for you :
> Rectangle :
> - length/width
> - length > 0, width > 0
> Square :
> - length/width
> - length > 0, width > 0
> - length = width

> I didn't define any "operations" because they aren't necessary.

Gee, I certainly see operations. If you aren't using / for div what
are
you using it for? If it is div then gosh most mathematicians consider
div to be an operation.

Most in Logic cal > and = relational operators

So there's a *lot* of operations as I can see.

> Not necessary because I can already "argue about their relation
> and apply the LSP" . I can already see a potential substitutability
> conflict between Rectangle and Square, and not one line of code
> has been produced yet.

I don't see problems where Square and Rectangle, as siblings, are
derived
from Quadrilateral or Shape.

I do not see a problme where Square or Rectangle inherit from the a
*Mutable* version of the other.

Nor do I see a problem where Square is kind of, or type of Rectangle
in
some page border creation program.

So just as Ram relates above there are problems nor cake walks for
that
matter, *unless* people incorrectly do as as Perryman does here, and
RMartin (RCM) does in the Square/Rectangle - Circle/Ellipse threads,
base
themselves upon 1 or 2:
  a.) philosophical idealist *a priori* conceptualization where a world
*preconceived* to be *some* way before the actual, concrete domain and
specific application within a domain is known.
   b). philosohical Kantian *dualism* where ideas, theory, in the one hand
and practice on the other are seen as mostly independent and separate
*streams*. Falsely versus the scientific method where ideas/theory
and
practice are properly understood as complementary sides of the same
coin,
where each indiviudally, and the 2 together, drive the other forward
in
dialectical interaction. Theory most often, or significantly leads,
or
guides and practice verifies theory. Where there is general
progress in both are wedded in cable that spirals and forms a
spatio-temporal helix. With Kantian dualism the essentially sees
theory
and practice as individually respectively driving itself forwrd for
the
most part. In this case one might posit as Perryman does above that
there are some kind of "immutable", "ever-present" properties that
things
like Squares and Rectangles have apart from any kind of concrete,
specific, really existing - in imagination like *some* maths, or the
real
world - domain and *then* within a domain some particular, concrete,
specific application.

Ram espouses real science here, Perryman a regressive, in one way or
another, mythical, viewpoint wholly in concert his historical neo
crafto-pragmatism. See my site for details on exactly why XP and
those
close to it and in essential agreement with it at bottom though not
quite
as *visibly* or *obviously* extreme, like Perryman, the "neo" is
a backward looking craftistry + Amercan Pragmatist (British
Empiricist)
software engineering trend.

Elliott 

-- 
OO software rests upon class abstractions expressed in class method
*behaviors*.  The sum of class method behaviors is the overall class
*role*.  Class role should have primary responsibility for managing
class
data such that the impact of class data is driven by the operation of
class methods.
         ~*~   Get with OO fundamentals, get OO.  ~*~
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               * http:\\www.radix.net/~universe *
          @Elliott 2003 my comments ~ newsgroups+bitnet OK
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******END REPOST
Elliott
-- 
Theory Leads, Practice Verifies

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