[whatwg] multiple itemtypes in microdata?
philipj at opera.com
Tue Jun 28 06:24:01 PDT 2011
On Mon, 27 Jun 2011 07:53:53 +0200, John Giannandrea <jgiann at google.com>
> In the user feedback from the schema.org proposal, which uses microdata
> its syntax, we have seen several use cases that would seem to require
> multiple itemtypes per itemscope.
> Currently the microdata spec only allows one itemtype which defines the
> meaning of the vocabulary for subsequent itemprops.
> Allowing an arbitrary list of itemtypes would not be desirable because
> a user agent would have to have knowledge of the type vocabularies in
> to parse the page.
Nothing needs to be known about the vocabulary in order to handle itemtype
currently, at least if by "user agent" you mean browsers and the DOM API.
In other words, allowing multiple types wouldn't be a problem here.
> We suggest that itemtype be changed to allow multiple space separated
> (just like itemprop), but only if the origin domain of the types is the
> same. This would allow a vocabulary provider to allow multiple types
> and to
> take responsibility for what the property vocabulary definition is in the
> context of more than one type.
The itemtype is supposed to be an opaque string, so it seems quite odd to
impose restrictions that require parsing the string to get the domain
name. In the case of schema.org, wouldn't it be quite helpful if people
extended it somewhere *other* than schema.org, so that it would be
possible to follow the itemtype URL and perhaps find some documentation of
the type? (Not necessary anything fancy, see e.g. http://n.whatwg.org/work)
In short, I think that simply allowing multiple types would be a workable
solution here, without any specific restrictions. The only change to the
DOM API would be making the itemType IDL attribute a DOMSettableTokenList,
just like itemRef and itemProp.
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