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Bug 14518 - Microdata: Can "the same vocabulary" span multiple domains?
Summary: Microdata: Can "the same vocabulary" span multiple domains?
Alias: None
Product: WHATWG
Classification: Unclassified
Component: HTML (show other bugs)
Version: unspecified
Hardware: Other other
: P3 normal
Target Milestone: Unsorted
Assignee: Ian 'Hixie' Hickson
QA Contact: contributor
Depends on:
Reported: 2011-10-20 08:54 UTC by contributor
Modified: 2012-07-18 18:48 UTC (History)
3 users (show)

See Also:


Description contributor 2011-10-20 08:54:54 UTC

Microdata: Can "the same vocabulary" span multiple domains?

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User agent: Opera/9.80 (X11; Linux x86_64; U; Edition Next; en) Presto/2.9.220 Version/12.00
Comment 1 Philip Jägenstedt 2011-10-20 08:58:49 UTC
As of itemtype can take multiple types as long as they "use the same vocabulary".

For validation purposes, is it possible for a vocabulary to span multiple domains, or could this always be flagged as invalid without vocabulary knowledge:

<x itemscope itemtype="">


(Yes, ideally the validator should have knowledge about these two vocabularies to provide much better validation, but then assume that two unknown itemtypes are used.)
Comment 2 Philip Jägenstedt 2011-10-20 09:01:05 UTC
Given that itemtype is an opaque string it would seem odd to treat it as a URL and apply validity constraints, but it would also seem odd for a validator to warn about what is most likely a violation of the "same vocabulary" constraint.
Comment 3 Philip Jägenstedt 2011-10-20 09:02:04 UTC
> warn about

typo: not be able to warn about
Comment 4 Ian 'Hixie' Hickson 2011-10-20 20:08:16 UTC
It wasn't my intent to have any limitation here. Is there any text that suggests that there is one?

I'd rather not encourage it (e.g. via an example), because it's rarely going to be correct.
Comment 5 Philip Jägenstedt 2011-10-21 07:44:52 UTC
No, there's no text suggesting anything, "same vocabulary" isn't defined at all. It would be nice if this question were answered in some fashion:

Should a validator complain about <x itemscope itemtype="">?

A note that sameness is defined by the vocabularies themselves and more importantly that it cannot be determined by deconstructing the (opaque) item type would suffice.
Comment 6 Ian 'Hixie' Hickson 2011-10-25 04:57:11 UTC
A validator should complain for:

   itemtype="" the same way that an XML vocabulary conformance checker would complain for an application/xml file that contains an unknown namespace.

That is, it should say "I'm sorry, I don't know how to validate this as I do not know that vocabulary".

Given that, the question asked in comment 5 is moot.

But I can certainly add a note saying that what a "vocabulary" is is defined by the document that defines a vocabulary, and thus that whether two types use the same vocabulary is defined by that vocabulary's spec, if it's not obvious. (It seems kind of obvious to me.)
Comment 7 Philip Jägenstedt 2011-10-25 09:02:13 UTC
No, that would be a bit circular. The spec does say that itemtype is an opaque string, so the conclusion should be clear. Given the rather small number of people implementing validators, perhaps deriving all possible conclusions is a bit excessive. I'll be happy with WONTFIX.
Comment 8 Ian 'Hixie' Hickson 2011-10-28 20:08:32 UTC
EDITOR'S RESPONSE: This is an Editor's Response to your comment. If you are satisfied with this response, please change the state of this bug to CLOSED. If you have additional information and would like the editor to reconsider, please reopen this bug. If you would like to escalate the issue to the full HTML Working Group, please add the TrackerRequest keyword to this bug, and suggest title and text for the tracker issue; or you may create a tracker issue yourself, if you are able to do so. For more details, see this document:

Status: Rejected
Change Description: no spec change

Ok. Please don't hesitate to reopen it if you can think of a way to make this clearer that isn't tautological and doesn't seem to encourage the practice.