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Many of the OO luminaries use encapsulation interchangeably with information hiding or link them closely. From the article you linked to I quote
"
* Cox'definition allows for encapsulation to reveal some information, for example full visibility to the procedures offered by object, while hiding some other information, for example no visibility to data.
* Booch and Rambaugh make no distinction between information hiding and encapsulation. "
I'll take the opinions of Brad Cox and Grady Booch over anyone who uses public member variables, C++ or arrays to argue points about OO. No offense to Berard, intended.
The truth about software engineering is that most of the core tennets around it are based on opinions, conjectures and best practices. Moore's law, Mythical Man months and Extreme Programming are all just theories and opinions. Some opinions believe information hiding is akin to encapsulation while others believe it is merely grouping things together. The former makes sense to me with regards to what I believe is effective object oriented programming while the latter does not.
Anyway this is rather offtopic for XML-DEV so email me offlist if you want to continue this discussion.
-----Original Message-----
From: Maciejewski, Thomas [mailto:Thomas.Maciejewski@lehman.com]
Sent: Tue 9/10/2002 11:12 AM
To: Dare Obasanjo; Maciejewski, Thomas; Henry S. Thompson; Jeff Lowery
Cc: paul@prescod.net; Xml-Dev (E-mail)
Subject: RE: [xml-dev] Subtyping in XML
I grabbed this snippet from:http://www.arcc.or.ke/ken_it1.htm
and although the definition of encapsulation is closely linked to
information hiding I am not sure if your argument that XML does not provide
information hiding eliminates it entirely from being used in combination of
the term OO. In any case here is a statement that at least throws a bit a
vagueness on the definition of encapsulation:
<quote>
According to Berard [Ber93], if encapsulation were the same as information
hiding, then one would argue that everything that was encapsulated was also
hidden. This is not true. For example, even though information may be
encapsulated within arrays the information is not hidden. Another example is
the creation os some global data in C++ class public interface, the data is
not hidden.
</quote>
so although XML doesn't hide data it seems that it can encapsulate and
promote the reuse of object like elements ????
-----Original Message-----
From: Dare Obasanjo [mailto:dareo@microsoft.com]
Sent: Tuesday, September 10, 2002 1:48 PM
To: Maciejewski, Thomas; Henry S. Thompson; Jeff Lowery
Cc: paul@prescod.net; Xml-Dev (E-mail)
Subject: RE: [xml-dev] Subtyping in XML
I'm not sure what definition of encapsulation you are using. Encapsulation
in OO is the seperation of an object's interface from it's internal data
structures and implementation. All XML documents have is internal structure
which have to be exposed to do anything with them.
-----Original Message-----
From: Maciejewski, Thomas [mailto:Thomas.Maciejewski@lehman.com]
Sent: Tue 9/10/2002 10:37 AM
To: Dare Obasanjo; Henry S. Thompson; Jeff Lowery
Cc: paul@prescod.net; Xml-Dev (E-mail)
Subject: RE: [xml-dev] Subtyping in XML
I think this may be because there seems to be a trend towards using
XML in
parallel with OO systems. ( serializing objects or to help bridge
a
relational data base and an objects )
As far as the Inheritance, Encapsulation, polymorphism argument :
Inheritance - it has it
Encapsulation - I think at least some elements are there
polymorphism - I guess your point here is that there is no action so
how
could there be polymorphism ... but since there is a lack of action
then
maybe the polymorphism part of this definition is irrelevant?
I definitely see XML at least aiding a good OO design ... picture a
system
of xml data that gets passed around a system of "strategy design
pattern"
type code that excepts this data in and is able to process what is
needed
and pass these "objects" on to something else.
Doesn't soap also push towards this paradigm? and why would this
not be OO
or at least a part of the OO paradigm?
While it may be arguable that XML is NOT OO I wouldn't get too upset
when
you hear OO in combination with XML unless you would like to see XML
limited
to non OO systems. In my opinion it this would be a major
limitation.
-----Original Message-----
From: Dare Obasanjo [mailto:dareo@microsoft.com]
Sent: Tuesday, September 10, 2002 1:20 PM
To: Henry S. Thompson; Jeff Lowery
Cc: paul@prescod.net; Xml-Dev (E-mail)
Subject: RE: [xml-dev] Subtyping in XML
Every time I read the words Object Oriented or the abbreviation OO
in
combination with XML, I cringe. Objects aren't XML and XML isn't
objects.
W3C XML Schema has some features inspired by OO but I wouldn't go as
far as
calling it OO in XML or even worse calling it an "Object Oriented
schema
language".
The core tennets of OO are encapsulation, inheritance and
polymorphism. W3C
XML Schema gives us 1 of these, once the XQuery REC + F & O are done
we'll
get another. Encapsulation I doubt we'll ever see given the way the
current
family of technologies works.
This is besides the fact that objects are about behavior not data
while XML
is the exact opposite.
-----Original Message-----
From: Henry S. Thompson [mailto:ht@cogsci.ed.ac.uk]
Sent: Tue 9/10/2002 10:08 AM
To: Jeff Lowery
Cc: 'paul@prescod.net'; Xml-Dev (E-mail); Dare Obasanjo
Subject: Re: [xml-dev] Subtyping in XML
> That's a bit of a strawman, IMHO. It may have been the
intent of
the WG to
> produce OO in XML
Not produce, but introduce, and I think you're both a little
off-target wrt why type definition by restriction and
extension are
in
the language. They're there in large part because the WG
had a
requirement to improve the managability of the process of
syntactic
constraint, by introducing 'inheritance' (read OO-design
features)
into the constraint language. Think of C --> C++ as a
parallel, in
so
far as C++ took a number of OO design patterns generally
acknowledged
to be useful for maintaining large programs over time, which
C
developers had to implement using text-substitution-macros
(i.e. #include), and moved them into the language. In
introducing
the
tag-type distinction, derivation by restriction and
extension, named
element and attribute groups and substitution groups, the WG
was
very
consciously trying to do the same thing, looking at existing
'best
practise' wrt the use of parameter entities in large DTDs.
You may or may not think we got it right, but that was the
primary
motivation. The possibility of a better impedence match
between
documents and application data was a collateral benefit (or
not, _ad
lib._).
ht
--
Henry S. Thompson, HCRC Language Technology Group,
University of
Edinburgh
W3C Fellow 1999--2002, part-time member of W3C
Team
2 Buccleuch Place, Edinburgh EH8 9LW, SCOTLAND -- (44)
131
650-4440
Fax: (44) 131 650-4587, e-mail:
ht@cogsci.ed.ac.uk
URL: http://www.ltg.ed.ac.uk/~ht/
[mail really from me _always_ has this .sig -- mail without
it is
forged spam]
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