Re: [Webmacro-devel] Revised #macro stack overflow test code

[Marc P. <ma...@an...>]

On Sun, 20 Apr 2003 12:48:26 -0700, Brian Goetz <br...@qu...> wrote:

>> Take an RSS news feed for example, typically these can contain up to 15 
>> news items. You may only want to display five of them. As the item nodes 
>> are usually under a channel node, this would be rather awkward to 
>> implement with a generic tree traversal directive.
>
> This is a good example, since it would be a common usage of any DOM
> traversal in WM and is pretty simple.
>
> Option 1: preprocess with a servlet and extract what you want.  This

As is probably abundantly clear, I do not favour options like this. This is 
because in many cases, particularly with the possible expansion of the WM 
user base to pure web-heads with no Java skills (via the webapp), people 
will need to / should be able to do stuff like this without coding Java.

> Option 2: Introduce a context tool that knows how to flatten trees into
> linear streams of SAX-like events:

Yuck-ish. A flattened tree is better than this, I think. As long as your 
node objects have a getParent() mechanism you can get an idea of your 
current node's relationship. The only problem here is that getting full 
parentage information would be difficult because we have no #break or 
#while loop.

> Option 3: Use XPath for selection.  Use an XPath select to whittle

Yes, or a similar mechanism

> Option 4: Some sort of traversal directive, which is going to end up
> looking a lot like XSL.  Combining it with XPath could be a win.

Yes - it doesn't have to be like XSL. One of the biggest problems with XML 
is its XSL template based non-linear approach. Very confusing for the 
author.

Have you seen XQuery? That is a template language for presenting XML data. 
It has a special syntax for expanding nodes by XPath query, based on the 
current node context. Of course I'm not proposing a new syntax for this, 
just showing what's out there. In XQuery you just write:

This is the title node under the current para node: $currentNode/$title

...interesingly XQuery is VERY like WM in some of its syntax! I would 
suggest an XQuery directive where you can embed XQuery script in a WM 
template, but the differences in syntax would be VERY annoying.

http://www.w3.org/TR/xquery/

Also, I am writing another message on these issues with a new thread 
subject...

-- 
Marc Palmer (Wangjammer5)
http://www.wangjammers.org
Java Consultants