[ZDP] BackTalk to Document The Zope Book (2.5 Edition)/Using Basic Zope Objects
Wed, 06 Aug 2003 01:06:38 -0400
A comment to the paragraph below was recently added via http://zope.org/Documentation/Books/ZopeBook/current/BasicObject.stx#1-0
When building a web application with Zope, you construct the
application out of objects. By design, different objects handle
different parts of your application. Some objects hold your content
data, such as word processor documents, spreadsheets and images.
Some objects handle your application's logic by accepting input from
a web form, or executing a script. Some objects control the way
your content is displayed, or *presented* to your viewer, for
example, as a web page, or via email. In general Zope objects take
three types of roles:
Content -- Zope objects such as documents, images and files hold
different kinds of textual and binary data. In addition to objects in
Zope containing content, Zope can work with content stored externally,
for example, in a relational database.
Logic -- Zope has facilities for scripting business logic. Zope allows
you to script behavior using Python, Perl, and SQL. "Business logic" is
any kind of programming that does not involve presentation, but rather
involves carrying out tasks like changing objects, sending messages,
testing conditions and responding to events.
Presentation -- You can control the look and feel of your site with
Zope objects that act as web page templates. Zope comes with a tag based
scripting language called the Document Template Markup Language (DTML)
to control presentation.
% Anonymous User - May 31, 2002 10:39 am:
This three types are a bit artificial. I agree with the CONTENT. I also agree on the LOGIC section. But I am
having some problems with the PRESENTATION layer. DTML (why did you not mention ZPT) is a mixture of LOGIC,
CONTENT and PRESENTATION.
After all I would say DTML belongs to the realm of LOGIC. It is a "programming" language and not "really"
responsible for PRESENTATION. It is a means of bringing content into a site... but like HTML which mixes
STUCTURE (<p></p> etc.) and PRESENTATION (<b></b>) it is neither fish nor flesh. CSS is an example for "pure"
I read an article that said, ZOPE had a problem with the separation of CONTENT - LOGIC - PRESENTATION. To me
it looks as if the explanation tries to show the opposite... well, it failed and creates an artifical and
wrong separation of CONTENT, LOGIC and PRESENTATION.
% Anonymous User - July 2, 2002 1:49 pm:
Can somebody confirm this: DTML is going away and ZPT will play a bigger role?
If this is the case, I don't want to learn DTML. Zope should have a section where both Zope and users can
post any new "trend" or future changes.
% Anonymous User - Aug. 21, 2002 10:39 am:
"...it is neither fish nor flesh."
Should be "neither fish nor fowl."
% hansa - Sep. 20, 2002 11:15 am:
Well, DTML is all of CONTENT/LOGIC/PRESENTATION, although only small chunks of CONTENT and LOGIC should be
used and larger ones factored out.
Templates synthesize the whole stuff into a (HTML) RESPONSE,
so the separation of CONTENT/LOGIC/PRESENTATION is somewhat artificial.
% Anonymous User - Nov. 29, 2002 11:44 pm:
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% Anonymous User - Aug. 6, 2003 1:06 am:
The seperation of content/logic/presentation has a history that predated Zope. This goes back (at least) to
the Model/View/Control deisgn of GUIs in SmallTalk. For a full review, read Design Patterns by Gamma et
al.(Addison-Wesley). The Zope developers are (very good) OO developers, and are using their terms quite
accurately. The seperation may seem artificial at this point, but if you have a large project you will
appreciate the seperation when you have to maintain or update the site.