From: Conrad Schneiker <schneik@...>
Date: 2001-03-23T15:47:53+09:00
Subject: [ruby-talk:13117] ZPT, a next-generation template technology (repost)

FYI. Thought some Rubies might be interested in this.

Subject: ZPT, a next-generation template technology
Date: Sat, 17 Mar 2001 01:43:50 -0000
From: "Hamish Lawson" <hamish_lawson@btinternet.com>
Newsgroups: alt.php, comp.lang.java, comp.lang.perl.misc, comp.lang.python

Hamish Lawson wrote:
> 
> The Zope Presentation Templates project is underway at Digital Creations
> to develop a next-generation template technology for Zope* that is
> XHTML-compliant and which makes it easier for designers to work with.
> However it is hoped to design it in such a way that as much as possible
> is not specific to Zope, in the belief that the technology is more
> widely useful and could be adopted by other languages and tools.
> Developers from other communities may want to consider contributing to
> the design of ZPT to help keep it language-independent, and to consider
> implementing the approach in their programming language of choice.
> 
> First of all some background on what is meant by "next-generation".
> 
> In the beginning programmers wrote program code with embedded HTML. Then
> technologies like eperl, ASP, PHP and JSP allowed us to reverse this and
> to embed program code in the HTML. However a school of thought wanted to
> have greater separation of presentation and logic, and so various
> template mechanisms were devised that provided just enough
> programmability to control presentation, but which moved the business
> logic out elsewhere. One example of this approach is Freemarker:
> 
>    <h1>$customername</h1>
>     <table border="1">
>         <tr>
>             <td>Date</td>
>             <td>Amount</td>
>         </tr>
>         <list deposits as deposit>
>             <tr>
>                 <td>${deposit.date}</td>
>                 <td>${deposit.amount}</td>
>             </tr>
>         </list>
>     </table>
> 
> Instead of custom tags some other template mechanisms use special
> markers to designate control structures, but in general most template
> mechanisms share the property that their templates are not compliant
> with XHTML (though the rendered output may be). As such it can be
> awkward trying to use such template mechanisms with authoring tools that
> only understand XHTML.
> 
> The approach that the ZPT project is pursuing is to attach the control-
> flow, formatting and placeholder directives as *attributes* of standard
> XHTML tags. The example above thus becomes something like:
> 
>     <h1 zpt:insert="customername">Bob Smith</h1>
>     <table border="1">
>         <tr>
>             <td>Date</td>
>             <td>Amount</td>
>         </tr>
>         <tr zpt:repeat="deposit deposits">
>             <td zpt:insert="deposit/date">01/02/2001</td>
>             <td zpt:insert="deposit/amount">23.40</td>
>         </tr>
>     </table>
> 
> Because this doesn't make use of special tags, but employs attributes
> instead, it should pass unscathed through most decent authoring tools.
> Moreover (borrowing an idea from Enhydra's XMLC template scheme) the ZPT
> template scheme allows typical sample content to be used as a proxy for
> the real data (which is substituted by the template engine), so making
> it easier to work with in an authoring tool.
> 
> More information on the rationale of attribute languages can be found
> 
>     http://dev.zope.org/Wikis/DevSite/Projects/ZPT/AttributeLanguage
> 
> An overview of ZPT can be found at
> 
>     http://www.zope.org/Wikis/DevSite/Projects/ZPT/VisionStatement
> 
> Hamish Lawson
> 
> * Zope is a leading open-source web application server and content-
> management framework, written in Python by Digital Creations.

Conrad Schneiker
(This note is unofficial and subject to improvement without notice.)