Re: Style Issue

Hi Tim,

Many thanks for the feedback!


On Wed, Jan 2, 2013 at 10:46 AM, Tim Cole <t-cole3@illinois.edu> wrote:

> I agree with your analysis that the previous solution for style has flaws
> that need to be addressed.****
>
> [...] but I worry a little about the minting of the new property
> oa:styleClass and thinking about how it will be used.
>

Agreed. I looked for existing RDF predicates, but didn't find any that were
appropriate.

**1.       **What are the implications for an annotation serialized in
> XHTML+RDFa (i.e., where the XHTML class attribute is intrinsically
> available for styling)? Do we have to mint our own styleClass property? Or
> could we more simply leverage the existing
> http://www.w3.org/1999/xhtml:class as the property?
>

Is that valid RDF? If it is, then I'm (personally) in favor of using it
instead of inventing our own identical predicate.  While I agree that it's
possible to use in other XML based contexts, I'd like to be certain it's
possible to import something defined as an XML attribute into RDF as a
predicate.

 2.       **The value of a styleClass property of a target or body resource
> is presumably in almost all cases specific to an individual annotation or
> finite set of annotations, right?
>

Yes.  Otherwise we could attach it to the resource directly, but then it
would be of global scope.  This would become problematic when there was an
annotation with a style that defined blocks for (say) "Body" and "Target",
and then two different annotations associate this blocks with the same
resource.  It could happen when a client has default styling rules it
applies, and the same client is used to create the two annotations.


> So the domain of oa:styleClass will always be (practically speaking)
> oa:SpecificResource? So you'd almost always use the oa:SepcificResource
> construction even in the absence of Selector, Scope and State?
>

Yes. And agreed that this is a shame, compared to the @document url() rule
construction, but ...


>  Probably moot because I can't come up with a practical use case where
> you'd want to apply style on a target or body that was not an
> oa:SpecificResource.
>
... it does seem like the appropriate compromise given this point.

Thanks again, and we would welcome any other feedback on this issue!


As a logistical point, we intend to make the new draft available to the
list for further feedback before the end of the week.  We would love to
then get feedback in order to publish it before the beginning of February,
and hopefully closer to the middle of January.

Many thanks,

Rob


*From:* Robert Sanderson [mailto:azaroth42@gmail.com]
> *Sent:* Thursday, December 20, 2012 10:15 AM
> *To:* public-openannotation
> *Subject:* Style Issue****
>
> ** **
>
> ** **
>
> Dear all,****
>
> ** **
>
> While writing up the new method of attaching Styles to Annotations, we ran
> into the following unanticipated issues.  We feel this makes the current
> solution for style unworkable, and propose a slight modification that
> should make things easier all round.****
>
> ** **
>
> Issues:****
>
> ** **
>
> 1.  Styles reference the resources in the graph by URI, using the CSS
> @document rule.  While this makes matching easy, it becomes impossible with
> the republishing method that is recommended in the specification.****
>
> ** **
>
> For example, a system publishes an Annotation A with an embedded body
> URN:B.  URN:B is thus the URI that is in the Style.****
>
> ** **
>
> A second system harvests the Annotation, republishes it at A2, and the
> body as a web resource at HTTP URI B2.  It should also assert that B2
> equivalentTo URN:B.  So now the style refers to the equivalent resource,
> not the body itself and systems will always have to check both.****
>
> This isn't the end, however, as this is likely to happen multiple times in
> a distributed system.****
>
> The Style could be updated, but it might be a web resource that is
> maintained outside of the annotation system and these changes would not be
> reflected in the copies.  It also relies on consuming systems to understand
> the content of Styles, which seems above and beyond what they should be
> expected to do.****
>
> ** **
>
> ** **
>
> 2.  As Styles refer to the URI of the resource, they cannot be re-used
> across multiple annotations.  This means that there necessarily must be one
> style per annotation, which is contrary to most uses of CSS and really to
> the web architecture in general.  So every system that has a style for its
> annotations must create a new style resource for each annotation, rather
> than just a default few.****
>
> ** **
>
> ** **
>
> 3.  Following from 2, there is no reason to *not* embed the style if it is
> tied 1:1 to the Annotation. This defeats the purpose of some of the changes
> from the first draft, eg to make it a valid CSS resource rather than just
> the value block.  It also brings up a (lesser) documentation/learning issue
> that to understand Styles you need to understand the Content in RDF model,
> which otherwise is not necessary.****
>
> ** **
>
> We consider the sum of these issues to be a show-stopper.****
>
> Our proposal for how to adapt it is:****
>
> ** **
>
> 1.  Keep the Style resource a valid CSS document attached to the
> Annotation, still using oa:styledBy, as in the current proposal.****
>
> ** **
>
> 2.  Instead of using the complex @document url() rule construction,
> instead use the more familiar class name construction.****
>
> ** **
>
> 3.  Have a property in the Annotation graph on the resources to be styled
> that records the class name.   Systems then match the property to the
> respective name in the CSS document.****
>
> ** **
>
> This solves Issue 1 because the property can be reattached easily to the
> new resource, just like all of the other properties and relationships.  At
> the same time, we use only basic CSS constructions rather than the CSS
> Level 3 @document construction.****
>
> ** **
>
> It solves Issue 2 because the class names can be re-used across multiple
> annotations.  I also makes it easier to swap styles across a range of
> annotations -- simply change the referenced CSS resource and they all
> change, rather than the current method (edit all of the embedded CSS blobs)
> or the first version (change the references on all of the Specific
> Resources).****
>
> ** **
>
> It solves Issue 3 by solving Issue 2, as the style is not tied 1:1 with
> the Annotation.****
>
> ** **
>
> Thus:****
>
> _:Anno a oa:Annotation ;****
>
>   oa:styledBy <Style1> ;****
>
>   oa:hasTarget <SpTarget1> ;****
>
>   oa:hasBody <Body1> .****
>
> ** **
>
> <SpTarget1> a oa:SpecificResource ;****
>
>   oa:hasSelector <Selector1> ;****
>
>   oa:styleClass "red" ;****
>
>   oa:hasSource <Target1> .****
>
> ...****
>
> ** **
>
> Where Style1 has the representation:****
>
> .red { color : red }****
>
> ** **
>
> This seems to capture the best parts of the current proposal while solving
> the issues that have come up with it.****
>
> ** **
>
> Please let us know any thoughts or comments on this revised approach.****
>
> ** **
>
> Many thanks,****
>
> ** **
>
> Rob, Paolo and Herbert****
>
>   ****
>