Justifying breaking backward compatibility based on existing content (was Re: RDF 1.1 Lite Issue # 2: property vs rel)

Hi Henri,

On Tue, Oct 25, 2011 at 4:00 AM, Henri Sivonen <hsivonen@iki.fi> wrote:

> On Sun, Oct 23, 2011 at 3:28 AM, Gregg Kellogg <gregg@kellogg-assoc.com>
> wrote:
> > There are probably some corner cases that would need to be worked out,
> but
> > by limiting this to the HTML+RDFa definition, we avoid backwards
> > compatibility issues with RDFa 1.0 and get that much closer
>
> I think efforts to fix RDFa are doomed if they try to be backwards
> compatible with RDFa 1.0 in the sense that any RDFa 1.0 input you can
> construct produces the same triples in an RDFa_fixed processor as it
> would in an RDFa 1.0 processor. If you choose that route, you don't
> get to *remove* any of the badness of RDFa 1.0. And *removing* badness
> of RDFa is the kind of fixing RDFa needs. (For example, the obvious
> conclusion one should make about the statistic Guha provided is that
> the rel attribute shouldn't participate in RDFa processing.)
>
> Note that HTML5 does not try to be backwards-compatible with the HTML
> 4.01 spec. It tries to be compatible with existing content. That is,
> it tries to be compatible with content that's actually on the Web--not
> with content that one could construct based on the HTML 4.01 spec.
>

Thanks for raising this point, Henri. You bring an interesting perspective.
I'm curious to know how similar decisions are made in the context of HTML5.
How does a public working group such a WHATWG (which afaik does not have the
resources to index the whole web) go about deciding what feature or markup
pattern can be dropped from a spec? Are there representative samples that
you use? or is it merely based on what feedback you get from people who
"show up" and give feedback to the working group? Do browser vendors such as
Mozilla have any ability to help here? What do you do about deep pages
hidden behind password or a noindex courtesy? Extrapolate the findings from
the public web? The RDFa WG is seeking ways to assess what patterns are used
or not used in the wild (tangible numbers or % tend to carry a lot of
weight) so any hint would help.

Steph.