Re: The "Presentation" Layer

["Aaron Bartell" <aaronbartell@xxxxxxxxx>]

> AND and serverside tech used in generating the UI

Walden, this is the key thing to put an "AND" on as you have.  Nathan, I
would consider many of the API's you have in your product the presentation
layer API's.  In my mind the presentation layer is responsible for a couple
of key things:

1) Mapping/getting data to/from the server language to the UI.
2) Spawning/handling events from the UI back up to/through the server
language to the controller.

In some ways is it maybe just as important to say what the View SHOULD NOT
do.  For example, in a lot of RPG-CGI stuff there are links that take you
from CGIPGM1 to CGIPGM2.  Or more specifically, CGIPGM1 will output a stream
of HTML that has a link on it, and when the user clicks that link it
immediately takes them to CGIPGM2 (vs. CGIPGM1).  This is in contrast to the
development practice I see in *many* (but not all) JSF approaches where most
times every single action a user takes against JSFPGM1 is returned to
JSFPGM1 and based on the evaluation of that action JSFPGM1 will do the
equivalent of a 301 redirect to get the user to the right next page.  To get
back to my original statement, the View SHOULD NOT be making directional
decisions (i.e. what page do I go to next?) but instead always hand events
back to the same program that produced the page.  When I say "SHOULD NOT"
that might be slightly purist because I don't follow that rule to a "T" as
sometimes the rule needs to be broken to make the framework meet business
needs.

HTH,
Aaron Bartell

On Wed, Jul 16, 2008 at 11:25 PM, Walden H. Leverich <
WaldenL@xxxxxxxxxxxxxxx> wrote:

> To me the bresentation layer would include the js and other client-side
> tech (flash/silverlight/etc) AND and serverside tech used in generating the
> UI (asp.net/jsp/php/etc). itZs not until you walk into the business object
> layer that you leave the presentation layer. But that brings us back to last
> weeks business objects thrfead :)
>
> As for frameworks. I LOVE prototype, but it's more of a plumbing layer than
> a UI toolkit. Generally I like to make my own clientside code, but prototype
> can turn dozens of lines of js into 1 and make it crossbrowser at the same
> time. Sam's a genius!
>
> I've got a function to make tables zebra striped complete with hover row
> highlighting that takes nothing more to use than adding the 'zebra' class to
> a table and making a ZebraPage js call at the end of the page (which is in
> my standard footer so I don't even need to remember to call it.) I think the
> entie thing is something like 10 lines of js because of prototype.
>
> -Walden
>
> -Walden
>
> --
> Sent from my wireless device.
>
> -----Original Message-----
> From: Nathan Andelin <nandelin@xxxxxxxxx>
> Sent: 16 July, 2008 19:06
> To: Web Enabling the AS400 / iSeries <web400@xxxxxxxxxxxx>
> Subject: [WEB400] The "Presentation" Layer
>
> What do people mean by the "view" or "presentation" layer?  In a Web
> application, I gather that it means the "stuff" that runs in a browser;
> normally HTML, CSS, and JavaScript.  Then add "stuff" that runs in browser
> plug-ins; like Flash and Silverlight.
>
> Some say that you can include stuff that's hosted or runs on the server,
> that generates browser output, or processes browser input.  That's probably
> about as far as you can stretch the "presentation layer".  At some point you
> need to distinguish "presentation" from "business" and "data access" layers
> if you're following a model-view-controller design pattern.
>
> My reason for raising this topic is because I've been reading and pondering
> about "rich" UI frameworks during the past week.  More specifically, I've
> been looking at Prototype, YUI (Yahoo User Interface Components), GWT
> (Google Web Toolkit), dojo, Ext js, MooTools, and Open Laszlo.  I've been
> talking with people who are getting into Adobe Flex & ActionScript.
>
> I've been investigating whether to invest time into mastering one of the
> toolkits, or to continue along my current approach of pairing HTML with CSS
> and a modest amount of JavaScript.
>
> I'm somewhat impressed with the UI widgets in Ext js.  To the point that I
> got out the JavaScript tutorial and started learning a JavaScript notation
> called Object Literals, which are used extensively in Ext js & Prototype,
> and allow developers to define object properties and methods using an
> abbreviated syntax.  Click http://www.radile.com/rdweb/temp/objects.htmlto see a  example of using "Literals" to define an object containing three
> properties and a method that writes the property values to the screen.
>
> If I were to adopt Ext js as a toolkit, I'd need to become proficient at
> writing code like that.
>
> On the other hand, Joe Pluta keeps proclaiming that with EGL, you don't
> need to learn how to write presentation layer code.  The workbench does it
> for you.
>
> Any thoughts?
>
> Thanks,
>
> Nathan.
>
>
>
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