[whatwg] itemtypes from same vocabulary
ehs at pobox.com
Wed Feb 13 08:29:05 PST 2013
I'm confused because it looks like Microdata currently allows multiple
itemtypes to be expressed:
The itemtype attribute, if specified, must have a value that is an
unordered set of unique space-separated tokens that are
case-sensitive, each of which is a valid URL that is an absolute URL,
and all of which are defined to use the same vocabulary. The
attribute's value must have at least one token. 
I am seeking clarification about what is meant by 'same vocabulary',
the rationale, and whether it can be relaxed.
On Wed, Feb 13, 2013 at 11:23 AM, Lin Clark <lin.w.clark at gmail.com> wrote:
> Itemtype cannot reference different vocabs. Here are two relevant
> discussions that I know of, one with Hixie and the other with the HTML Data
> Task Force.
> On Wed, Feb 13, 2013 at 11:18 AM, Ed Summers <ehs at pobox.com> wrote:
>> Hi all,
>> I am looking for some guidance about the use of multiple itemtypes in
>> microdata , specifically the phrase "defined to use the same
>> vocabulary" in:
>> The item types must all be types defined in applicable specifications
>> and must all be defined to use the same vocabulary.
>> For example, does this mean that I can't say:
>> <div itemscope itemtype="http://acme.com/Foo http://zenith.com/Bar"> ...
>> The reason I ask is that there is some desire over in the schema.org
>> community  to provide a mechanism for schema.org to be specialized.
>> For example, in the case of an audiobook:
>> <div itemscope itemtype="http://schema.org/Book
>> http://www.productontology.org/id/Audiobook"> ... </div>
>> The idea being not to overload schema.org with more vocabulary, and to
>> let vocabularies grow a bit more organically. This schema.org group is
>> currently thinking of using a one off property additionalType that
>> would be used like so:
>> <div itemscope itemtype="http://schema.org/Book">
>> <link itemprop="additionalType"
>> I personally find this to be kind of distasteful since it replicates
>> the mechanics that microdata's itemtype already offers.
>> So, my question: is it the case that itemtype cannot reference types
>> in different vocabularies like the example above? If so, I'm curious
>> to know what the rationale was, and if perhaps it could be relaxed.
> Lin Clark
> Drupal Consultant
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