Re: Display requirements

From: Stefano Mazzocchi <>
Date: Wed, 01 Sep 2004 15:51:36 -0400

Chris Bizer wrote:

[snip 'cause nothing significant to add]

> 10. Additional fixed display elements
> It should be possible to specify additional fixed, data intependent display
> elements like headers and footers, company logo, explanations to certain
> sections, e.g. "This is a list of all projects for which the person is
> currently working".

hold it! This is where I have a problem: I think you want a template
language for RDF in RDF.

What I would like to have is a declarative visual ontology but
definately *NOT* a procedural template language since there are already
so many out there.

The fact is that foaf:person cannot be visualized because there is no
visual information (therefore, you cannot decide how to present this).

You said "cascading RDF stylesheets" and that hits the nail on the head,
but when you say "you must also have the company logo", that freaks me out.

one thing is to have "content" in the CSS level (very useful in :before
and :after CSS selectors), because, for example, "Warning: " before a
<warning>...</warning> element is style, not content.

But a company logo, a header, a footer, they are al content, not style
and content should be dealt with a template language, not a stylesheet
language and I really think that writing a template language in RDF that
would be abstracted from the actual presentation markup would be
*waaaaay* abusive (and would reinvent half a dozen wheels)

> 11. Handling of Missing Values
> It should be possible to specify alternatives for missing values e.g.
> display foaf:firstname and foaf:last name if foaf:name is missing. Or
> display dc:title if rdfs:label is missing.

Again, same thing: conditionals are not part of style because
conditionals are procedural not declarative.

It is not up to the 'display ontology' to indicate "what" information
should be there, but "how" the information present should be displayed.

Mixing these concerns is just like repeating the <font> HTML tag mistake
over again.

> # -----------------------------------------------
> # 2. Use Cases
> # -----------------------------------------------
> Potential use cases for a RDF display ontology.
> 1. Display RDF local data with a text-/graphic- and resource-oriented
> browser
> (like LongWell, Haystack, AnSeB) using one application-specific ontology
> and one
> set of style sheets.
> 2. Display RDF distributed data with a text-/graphic- and resource-oriented
> browser
> (like LongWell, Haystack, AnSeB) using different application-specific
> ontologies and
> multiple sets of style sheets provided by different authors.
> 3. Render RDF data as a text-oriented report (e.g. PDF)
> 4. Render RDF data as a graph (e.g. SVG, like IsaViz)

> 5. Edit an RDF graph
> I'm mostly interested in use case 1 and 2. But it would be nice if
> our ontology would also fit for the other use cases or at least
> would be extensible for the other use cases.
> Maybe we should rule editing out of scope for the first version.

Agreed, 5 is overkill at this point.


> What do you think about also inviting Damian Steer (
> to this discussion. He might also have
> interesting additional ideas.

Totally. Damian is fully aware of longwell and might have good input for us.

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 Wed Sep 01 2004 - 19:51:36 EDT

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