Xenon and Fresnel

From: Chris Bizer <chris_at_bizer.de>
Date: Mon, 6 Dec 2004 11:26:43 +0100

Hi everybody,

I was talking to Dennis Quam at ISWC in Japan about bringing people together
in order develop an RDF display vocabulary.

He has developed an alternative approach to Fresnel called Xenon which is
more XSLT oriented. A paper submitted to WWW2005 about Xenon is attached to
this mail.

We were discussing how Xenon and Fresnel could fit together (see mails
below) and Dennis proposed, that Xenon could be used to implement Fresnel.
Interesting direction ...

What do you think?
What do you think about Xenon?

Ryan: I saw in the SIMILIE repository that, you started implementing Fresnel
(http://simile.mit.edu/repository/fresnel/). What is the context of this
work? What's the timeframe?

I was also talking about Fresnel with some guys who were presenting semantic
portals at ISWC. They had similar, less expressive and more ad-hoc display
languages in their portals and were very interested in Fresnel. It seams
like many people are seeing the need for agreeing on a display language and
we could get some adopters easily, if we were coming up with something
flexible, but easy to use ....



>----- Original Message -----
>From: Dennis Quan
>To: Chris Bizer
>Cc: karger_at_theory.csail.mit.edu
>Sent: Sunday, December 05, 2004 8:47 PM
>Subject: Re: Fw: Xenon and Fresnel

>Hi Chris,
>I'm in Australia this week so sorry for my late reply.
>Forwarding the paper on to your colleagues is fine.
>The thought I had when I initially got your e-mail was that we could
>implement something like Fresnel in Xenon. It isn't >necessarily the case
>that the Xenon-level of expressiveness would have to be exposed to the
>developer, but for when deeper >customizations would be needed, then the
>expressiveness would be available. I agree completely that developers
>should be >provided with a level of expressiveness that suits the kind of
>problem they are tackling.
>Best regards,
>> Hi Dennis,
>> thanks for the paper and sorry that I'm answering so late. I was visiting
>> friend in Osaka and just came back to Germany Thursday.
>> I read your paper: Very interesting and very flexible approach but also
>> quite different from what we did with Fresnel. Some initial thoughts:
>> I totally agree with the goals which your are formulating in section one,
>> paragraph 5 and also like your abstract model in section 2. Especially,
>> idea of a "template marketplace" and the loose coupling between templates
>> using roles. I think giving the user the possibility to choose between
>> different representation is also very important and one of the key
>> of Fresnel.
>> Section 3 is the point where our approaches start differing. You build on
>> the ideas of XSLT, which results in a functional template language. Our
>> ideas are building more on HTML (= saying straight forward what to
>> display
>> in which order using the lens vocab) and CSS (=saying how to display it,
>> with the style vocab). Thus your language is functional, ours is
>> declarative.
>> We also tried to separate between content selection (what to display) and
>> styling (how to display it). You are mixing both, having language
>> like xhtml: LI or xhtml:TR woven in your templates.
>> Within your language, the stylesheet author works relatively close to the
>> output syntax (or at least your examples suggest this). Fresnel tries to
>> work on a higher level of abstraction, just declaring what to display
>> together, and leaves it to the rendering engine to produce concrete
>> output
>> for different syntaxes like HTML or SVG.
>> Short fresnel example (I don't know if you read the current specs):
>> :StandardLens rdf:type lens:StandardLens ;
>> rdfs:label "Standard Lens for FOAF persons" ;
>> lens:lensDomain foaf:Person ;
>> lens:showProperties [ rdf:type rdf:Seq ;
>> rdf:_1 foaf:name ;
>> rdf:_2 foaf:surname ;
>> rdf:_3 foaf:depiction ] .
>> Saying straight forward which properties to display. And:
>> :StandardStyle rdf:type style:style:DisplayStyleProperty ;
>> rdfs:comment "Root style for all properties. Used if nothing else
>> specified.";
>> :styleDomain rdf:Property ;
>> style:cssHook "StandardTextCssStyle" ;
>> style:attribute style:ShowLabel ;
>> style:attribute style:DisplayAsLink ;
>> style:attribute style:MultiValue ;
>> style:attribute style:MultiLine ;
>> style:group :FOAFStyles .
>> Saying how to display the properties.
>> The interesting question is now: Which of our approaches fits which
>> requirements?
>> I thing your language (being functional) is more expressive than our
>> declarative approach. But you are buying this flexibility with quite some
>> complexity. My idea with Fresnel was to keep things as simple as possible
>> order to make it easier for users to learn the language. Most people
>> understand HTML and CSS, but I know quite some which are having problems
>> with XSLT. All information about a lens is kept in one place in Fresnel.
>> Xenon it is spread over several templates, which makes thinks flexible
>> but
>> quite complex to understand.
>> As I already said at ISWC, we are using an RDFpath like selector
>> language,
>> where you are using SPARQL.
>> ?TARGET/_at_vCard:TEL [
>> Most of your example queries aren't to complex and don't use the
>> expressivity of SPARQL. So it might be an idea to switch to RDFpath in
>> to achieve better readability.
>> I would like to forward your paper and my initial comments to the others
>> involved in the Fresnel development and see what they think about Xenon.
>> Is this OK with you?
>> Chris

Received on Mon Dec 06 2004 - 10:26:56 EST

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