[Bug 13527] New: Microdata doesn't allow marking up content with multiple vocabularies

http://www.w3.org/Bugs/Public/show_bug.cgi?id=13527

           Summary: Microdata doesn't allow marking up content with
                    multiple vocabularies
           Product: HTML WG
           Version: unspecified
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: normal
          Priority: P2
         Component: HTML Microdata (editor: Ian Hickson)
        AssignedTo: ian@hixie.ch
        ReportedBy: richard@cyganiak.de
         QAContact: public-html-bugzilla@w3.org
                CC: mike@w3.org, public-html-wg-issue-tracking@w3.org,
                    public-html@w3.org


There are situations where content authors have the choice between multiple
overlapping microdata vocabularies. For example both schema.org/PostalAddress
and vCard are available for marking up postal addresses. Microdata forces
content authors to either choose one of them (schema.org because that's what
Google supports), or to duplicate their content.

The challenge with supporting multiple vocabularies in microdata is how to
associate property names with the vocabularies in absence of vocabulary
knowledge. This difficulty has been stated as the reason for rejecting a
similar issue here:
http://www.w3.org/Bugs/Public/show_bug.cgi?id=13470

The ambiguity can be avoided by generating multiple items from a single
itemscope, with one type each. For example:

<div itemscope>
    <span itemprop="streetAddress street-address">26 Dun Aengus</span>,
    <span itemprop="addressLocality locality">Galway</span>,
    <span itemprop="addressCountry country-name">Ireland</span>.
    <meta itemprop="altitem" content="http://schema.org/PostalAddress
streetAddress addressLocality addressCountry">
    <meta itemprop="altitem" content="http://microformats.org/profile/hcard
street-address locality country-name">
</div>

The altitem property would have to be a microdata built-in property that
affects microdata parsing. Its value would be a whitespace-separated list; its
effect would be to generate a new “alternate item” whose itemtype is the first
URL from the list. The rest of the list are property names to be copied from
the itemscope. The result here would be three items; one untyped item with
eight properties; one schema.org typed item with three properties; one vCard
typed item with three properties. This proposal is fleshed out here:
http://richard.cyganiak.de/blog/2011/08/multiple-itemtypes-in-microdata/

The point of this example is to argue that support for multiple vocabularies in
microdata is possible in a way that is more convenient to authors than forcing
them to repeat content.

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Received on Tuesday, 2 August 2011 19:37:08 UTC