Re: XUL Templates and Fresnel ...

From: Stefano Mazzocchi <>
Date: Thu, 28 Apr 2005 10:24:41 -0400

conor dowling wrote:
> I've been reading this mail group over the last two weeks with great
> interest. After using the current generation of XUL templates to build
> an RDF-driven display (see:
>, I could see a lot
> of functionality described here and in the Fresnel spec that XUL
> templates sorely lack. I think that their main omission, besides the
> lack of remote queries, is support for wildcards and defaults - they
> need a fallback to grab all properties and use OWL labels to enable
> compact but powerful displays.
> There's a new XUL template proposal (see:
>, one that allows for a
> variety of Query Processors. One could be a Fresnel Lens interpreter,
> encompassing the tree construction and label handling that's had quite
> an airing on this group recently. However, the proposal leaves the
> builder - the part of the template that fills in XUL elements - largely
> as is. This isn't sufficient for Fresnel on two grounds I think:
> - the tree of resources and properties that passes from a Query
> processor to the Builder is insufficient. It doesn't have a display
> label field for each property. To allow for a Fresnel Query Processor,
> every property in the tree should support that field. The builder must
> support it too: it needs to be able to extract and use the label field,
> support the likes of <label value="?predicate-label">
> - the builder itself can't handle any old list of property values. It
> only likes explicitly identified properties. It needs to support value
> wildcards, to allow something like <label value="?*"> where "*" stands
> for the value of any predicate.
> BTW, I'm sure there are many other requirements too - my knowledge of
> Fresnel is very limited.
> So what? Well, people could play around with Fresnel interpreters in
> Firefox (I wrote up a crude list of things for a lite processor at
> query.html) if, along with upgraded templates to handle a variety of
> Query Processors, came an enhanced template builder. This would help
> XUL and so help Firefox and I think it would help Fresnel too.
> Has anyone on the list looked at the XUL template spec?

I had not and I'm very happy that you pointed me in that direction.

After a complete-but-not-super-detailed read, I see strong overlap in
the design methodology and partial (but very interesting!) overlap in
the functional capabilities.

I personally think that the mozilla folks used RDF for a long time but
never really got it, they use it as a sort of mergeable property files
on (big!) steroids. Their templates reflect that: they are pretty solid
on the UI side (actions, bindings, UI widgets and all that) but lacking
in the RDF selection and graph->tree generation (which doesn't surprise
me: you hit that wall only after a while).

If XUL templates were to support, say, XPath queries over a DOM (as they
mention), then my vision of Fresnel would fit perfectly: fresnel would
do the graph selection and graph->DOM manipulation, and XUL templates +
mozilla will do the rest. Having a fresnel XPCOM component in mozilla
that does graph->tree rendering would be the only thing needed for this
to happen.

At the end of the day, XUL templates + mozilla achieve the exact same
functionality than velocity + servlet engine + HTML + CSS + javascript +
web browser, so they reside in the same space of the workflow: right
after the bridging between graph-world and tree-world.

XUL templates, to me, represent a perfect example of why we should stop
illuding ourselves that we can declare everything people will need from
RDF presentation and just work to bridge existing solutions between the
two worlds.

Stefano Mazzocchi
Research Scientist                 Digital Libraries Research Group
Massachusetts Institute of Technology            location: E25-131C
77 Massachusetts Ave                   telephone: +1 (617) 253-1096
Cambridge, MA  02139-4307              email: stefanom at mit . edu
Received on Thu Apr 28 2005 - 14:23:48 EDT

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