[Arp] The right way to use VO/TO's

[Zoltan Csibi]

Hi Chris

Let us call it for simplicity a "three-tier client/server architecture"
where the client implements the presentation logic, the business logic is
implemented on an application server and the data resides on database
server...this is the case we started to discuss

The sample application is the "Pizza Service" application. The business
logic is to place an order.

How the user interface handles collecting of info, shipping address etc is
not a business logic (the only aspect here which has to do with the business
logic is "how the business communicates with the consumers", how to layout
info).

How the datagrid works and what features it has is not a business logic.
It's a just a "framework" used for presentation.
Tomorrow I may add an HTML presentation layer for people not using Flash, or
a desktop application.

I am not saying that you cannot move part of the business logic to the
"framework" used for presentation layer...but that should not be considered
the cleverest solution.
The example would be the client-side validation issue...Once you split your
business logic like this, that means you cannot connect other presentation
layer/or application to your business logic without writing twice the
validation. (of course that may seem ok if you never intend to....)

And taking your sample with the Datagrid "mini application" and other
"ecosystems"...I should go further and say that even a simple Windows button
or window is a mini application! There is no single pixel on my screen which
is not a mini-application!

Zoli

-----Original Message-----
From: Arp-bounces at ariaware.com [mailto:Arp-bounces at ariaware.com] On Behalf
Of Chris Velevitch
Sent: Friday, March 17, 2006 2:33 PM
To: General List for Ariaware RIA Platform users and developers
Subject: Re: [Arp] The right way to use VO/TO's

On 3/17/06, Zoltan Csibi <zoltan at thesilentgroup.com> wrote:
> Chris...and why bother writing that email?
>
> Matt was talking about architecture, presentation layer as in

In an N-tier application, regardless of what the value of N is, Flash is not
the the presentation layer. Yes, we are talking about architecture and the
architecture creates the concept of the presentation layer (views), Flash
implements the presentation layer.
Flash also implements the rest of the architecture: controllers, commands,
service locator's, services, business delegates value objects, model
locator, etc.

> http://www.macromedia.com/devnet/flash/articles/flash_databases.html

This article is a bit dated as it refers to the capabilities of Flash 6.

Quoting from the ARP manual, page 1, paragraph 1:-

"One of the biggest problems facing Rich Internet Application (RIA)
developers today is how to architect their applications so that they are
maintainable, scalable and can be efficiently developed in a team
team-environment."

No matter thinly you slice the client tier of any N-tier client/server
application, you will be still be using a framework to architect that tier.
And then, via the framework, you'll layer the application in a maintainable,
scalable way. And one of those layers is the presentation layer.

> "What is the backend anyway? Isn't it just a web-based 
> database?"...NO, IT IS NOT

Most N-tier applications interact with some persistent storage mechanism.
And given the delivery mechanism of Flash applications, most, if not all,
storage is web based. Granted, in a really large N-tier (N>4) applications,
some tiers are not database tiers, but tier N is the client of a (N-1)-tier
database application. In the end there's a database of some sort somewhere
on the web.

> "We're all building database applications using a client/server 
> model"...We're all building less and less applications using a 
> client/server model and more applications using N-tiered architecture

All N-tiered applications are client/server applications.

> "Do you use any of the Flash components? What about all the business 
> logic bulitin to each component?"...What is the "business logic" built 
> into the components? What is "business logic"?

"business logic" is the way you want the application to work for a given
problem. Components are an "off-the-shelf" sub-applications.
Take the DataGrid. With a datagrid you can have user-driven column sortings,
cells can be editable or not, you render complex structures in a cell, you
can change the skin, etc. A DataGrid is a highly complex application in its
own right and is programmed by changing specific attributes to make it solve
your problem.

Even a 1-tier application is fractually an N-tier application.

Flash is a platform for developing/delivering applications, not a
presentation layer. The presentation layer is a concept in architecture of
an application.

I apologise, if I'm not clear about what I'm trying to say.


Chris
--
Chris Velevitch
Manager - Sydney Flash Platform Developers Group www.flashdev.org.au

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