Re: additionalType property, vs extending Microdata syntax for multiple types

Microdata has no machine readable way of specifying things like domain and
range.

So, I don't see how this will break any parser.

guha

On Mon, Jun 18, 2012 at 11:31 AM, Egor Antonov <elderos@yandex-team.ru>wrote:

> Using this property we do break microdata compatibility, because it's no
> longer microdata standard, but already such unofficial and undescribed fork.
> No parser will parse it without some coding work, no verifier tool can
> verify schema match, because it won't be microdata anymore.
> You propose to say "if you use microdata and want multiple itemtypes, use
> microdata with some hack"
> I propose the same thing, but naming it direct.
> It's just a superset of microdata features, and it can be implemented in a
> prettier way than "additionalType" property IMHO
> Or my logic is wrong?
>
> 18.06.2012, 21:46, "Dan Brickley" <danbri@danbri.org>:
> > On 17 June 2012 00:41, Guha <guha@google.com> wrote:
> >
> >>  My personal preference is to just add an attribute called type (or
> >>  additionalType) which is samePropertyAs rdfs:type and be done with it.
> >
> > I've come to the same view; see proposal below.
> >
> > I've just spent a little while trying to answer my "What would break?"
> > question, ... if we went the other way and extended Microdata. My
> > conclusion is that the safest and most responsible option is to define
> > http://schema.org/additionalType as a convenience alias for W3C's
> > http://www.w3.org/1999/02-22-rdf-syntax-ns#type property. If Microdata
> > was purely a syntax, maybe we'd be ok. But there is also another spec,
> > the Microdata DOM API. Some software, e.g. Opera-based browsers, have
> > been shipping with Microdata DOM API for a while. Others, like
> > Firefox, have just added support.
> >
> > http://my.opera.com/ODIN/blog/2011/12/06/hello-opera-11-60
> > http://dev.opera.com/articles/view/microdata-and-the-microdata-dom-api/
> > https://twitter.com/FirefoxNightly/statuses/210300933056380928
> > https://bugzilla.mozilla.org/show_bug.cgi?id=591467
> >
> > I made some tests with Opera 12, using
> >
> > <section itemscope itemtype="http://schema.org/CreativeWork
> > http://schema.org/Cat">
> > <h1 itemprop="name http://example.com/fn">Hedral</h1>
> > <p itemprop="description
> > http://purl.org/goodrelations/v1#description">Hedral is a male
> > american domesticshorthair, with ...</p>
> > </section>
> >
> > ...but couldn't retrieve the DOM node when multiple types (of any
> > kind) were present. Looking at the Firefox Bugzilla entry, there is
> > also active discussion there of multiple item types - not clear even
> > if basic multi-typing is supported yet.
> >
> > While we could choose to read this as "microdata API implementations
> > are still catching up with the current html spec, so more changes
> > wouldn't matter", I think the correct lesson is that we shouldn't
> > casually mess with markup design that could have complex and
> > un-analyzed impact on associated APIs. Browser makers will not
> > appreciate changes at this time, and it will be costly and
> > unproductive to try to persuade them. Any changes to Microdata would
> > have to include not only rules for the syntax, but a corresponding API
> > redesign, including failure conditions, new test cases etc., not to
> > mention the energy and engagement needed to persuade all relevant
> > stakeholders to accept the new model.
> >
> > I just don't think it's feasible, so let's try to do the best we can
> > with 'additionalType'.
> >
> > A concrete proposal:
> >
> > Property: additionalType
> > samePropertyAs: rdf:type
> > description: "An alias for the rdf:type relationship between something
> > and a class that the thing is in. It is generally preferable to use
> > syntax-native typing mechanisms. The additionalType construct can be
> > useful in constrained syntaxes - e.g. microdata - where multiple types
> > from
> > independent vocabularies cannot be easily expressed. In such
> > situations, care should be taken to assign the most relevant
> > schema.org type using
> > the primary (e.g. 'itemtype') typing syntax. Schema.org tools may have
> > only weaker understanding of extra types, in particular those defined
> > externally."
> >
> > Peter & co. - can you live with that?
> >
> > Dan
>
> --
> Egor Antonov
> http://staff.yandex-team.ru/elderos
>