W3C home > Mailing lists > Public > public-vocabs@w3.org > June 2012

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

From: James M Snell <jasnell@gmail.com>
Date: Tue, 19 Jun 2012 07:58:23 -0700
Message-ID: <CABP7RbfbmkfEXQQsUVZj2bdzM8dFG+B8dPm9zd=7F_NZoiGJBQ@mail.gmail.com>
To: Dan Brickley <danbri@danbri.org>
Cc: public-vocabs@w3.org, "Martin Hepp (UniBW)" <martin.hepp@ebusiness-unibw.org>, Peter Mika <pmika@yahoo-inc.com>, Ramanathan Guha <guha@google.com>, Jeni Tennison <jeni@jenitennison.com>
I know there has been quite a bit of discussion around this already,
and I cannot really speak for the microdata use cases, but I do work
with the activity streams format [1] and we've had a number of recent
discussions around the use of schema.org properties within a JSON
Activity Stream... AS has it's own basic type model (and "objectType"
property whose value is either a simple label representing known types
or an absolute IRI to identify types from other vocabularies. Having a
"type" property in the schema.org vocabulary would help us
tremendously in bridging the AS model into the schema.org realm. I'd
certainly be in favor of introducing it. ("additionalType" works too).

[1] http://activitystrea.ms

- James Snell

On Fri, Jun 15, 2012 at 11:26 AM, Dan Brickley <danbri@danbri.org> wrote:
> HTML5 Microdata, as defined in
> http://www.whatwg.org/specs/web-apps/current-work/multipage/microdata.html#encoding-microdata
> ... has only limited support for describing multiple types that
> something belongs to. In particular it requires they are described
> using a single schema.
> For Good Relations integration (and other scenarios) people have asked
> for a way of listing more types within schema.org markup.
> * One model is to use RDFa 1.1 (Lite), where this is quite natural.
> * Another is to add (as a workaround) a new property, e.g. called
> 'type' or 'additionalType', to schema.org's vocab (Martin requests
> this in http://www.w3.org/wiki/WebSchemas/GoodRelations )
> * A 3rd is to stretch
> http://www.whatwg.org/specs/web-apps/current-work/multipage/microdata.html#items
> to allow different namespaces to be used.
> The note at http://www.w3.org/TR/html-data-guide/#multiple-types-microdata
> discusses just this issue.
> I'm sending this as followup from discussion amongst schema.org
> partners, who welcome community advise on this point. Should we add a
> 'type' property to schema.org, try to change or stretch microdata
> syntax, ... or encourage people who want multiple diverse types to use
> RDFa Lite instead?
> Dan
> Copied below is the current Microdata / HTML5 spec text,
> "The item types of an item are the tokens obtained by splitting the
> element's itemtype attribute's value on spaces. If the itemtype
> attribute is missing or parsing it in this way finds no tokens, the
> item is said to have no item types.
> The item types must all be types defined in applicable specifications
> and must all be defined to use the same vocabulary.
> Except if otherwise specified by that specification, the URLs given as
> the item types should not be automatically dereferenced.
> A specification could define that its item type can be derefenced to
> provide the user with help information, for example. In fact,
> vocabulary authors are encouraged to provide useful information at the
> given URL.
> Item types are opaque identifiers, and user agents must not
> dereference unknown item types, or otherwise deconstruct them, in
> order to determine how to process items that use them.
> The itemtype attribute must not be specified on elements that do not
> have an itemscope attribute specified."
Received on Tuesday, 19 June 2012 14:59:13 UTC

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