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Re: CreativeWork can't be a Product?

From: Martin Hepp <martin.hepp@ebusiness-unibw.org>
Date: Tue, 8 Oct 2013 08:32:03 +0200
Cc: Aaron Bradley <aaranged@gmail.com>, Dan Scott <dan@coffeecode.net>, Chilly Bang <chilly_bang@yahoo.de>, Public Vocabs <public-vocabs@w3.org>
Message-Id: <2D52EFB9-D9C6-4AE3-9439-20AAE2E4B164@ebusiness-unibw.org>
To: Wes Turner <wes.turner@gmail.com>
On Oct 8, 2013, at 12:19 AM, Wes Turner wrote:

> Is this what http://schema.org/additionalType is for?

additionalType was mainly designed as a simple utility property so that one could use multiple types from *multiple* vocabularies in Microdata syntax.

Back then, we faced the need of being able to say that something is e.g. a http://schema.org/Product but keep the information that it is also something more specific, in particular keep type information from GoodRelations extensions (see also [1] and [2]), like

1. Wikipedia entries as type identifiers
* http://www.productontology.org

2. Cars, boats, bikes, etc.: The Vehicle Sales Ontology (VSO)
* http://purl.org/vso/ns

3. freeClassOWL - Construction and building materials
* http://www.freeclass.eu/freeclass_v1

Now, in RDFa, multiple types are straightforward, while in Microdata, multiple types work only if they stem from the same vocabulary, also because in Microdata, the type determines the applicable properties (other than in RDF; domain and range are very complicated notions in RDF).

Since, due to political reasons, it seemed unlikely that we could quickly get the Microdata spec updated, we added this utility property.

For most practical purposes, additionalType simply means this entity also has the secondary type or types.

Note, however, that if you want to mix types from the schema.org namespace (e.g. CreativeWork and Product) in Microdata syntax, it is cleaner to use the multiple type syntax of Microdata (all in the itemtype property, separated by spaces), since additionalType does not allow you to apply all properties from the additional type to the entity. Some validators might complain.

A positive side-effect of additionalType is that you can indicate which one is the most important, main type, and which ones provide just additional specificity. 


[1] http://wiki.goodrelations-vocabulary.org/Documentation/Extensions
[2] http://wiki.goodrelations-vocabulary.org/Vocabularies

> -- 
> Wes Turner
> On Mon, Oct 7, 2013 at 3:46 PM, Aaron Bradley <aaranged@gmail.com> wrote:
> Dan's solution and Martin's link are excellent ones.  Just a quick FYI a previous discussion and a proposal related to it provide some further information on this type of conundrum in schema.org:
> http://lists.w3.org/Archives/Public/public-schemabibex/2013Jan/0182.html 
> http://www.w3.org/wiki/WebSchemas/SchemaDotOrgMetaSchema
> A fragment from the former reference:
> > Assuming they take OWL seriously, they would infer new types for the
> > entity if properties were mixed and matched. If example, if the claimed
> > type is schema:Book and somebody used the schema:sku property, they
> > could infer it is also a schema:Product.
> On Mon, Oct 7, 2013 at 1:37 PM, Dan Scott <dan@coffeecode.net> wrote:
> On Mon, Oct 07, 2013 at 09:16:01PM +0100, Chilly Bang wrote:
> Hello!
> i'm busy at the moment with marking up with microdata of an online bookstore and realized the following dilemma:
> if a page is about describing and selling of a CreativeWork/Book, so i come to selling properties with itemprop="offers" itemscope="" itemtype="http://schema.org/Offer". But on this way i can't describe the book i sell like Product, with product's properties - i can't find any passage from CreativeWork to Product. There is in fact a passage from Offer to Product, with itemprop="itemOffered" itemscope="" itemtype="http://schema.org/Product", but repeating isn't a good way, beside of this it isn't easy to get such passage into html, even with itemref.
> I see no possibility to go the way CreativeWork->Product->Offer (or CreativeWork->Product and CreativeWork->Offer), but only CreativeWork->Offer, or Product->Offer. CreativeWork can't be a Product or am i wrong?
> Imho CreativeWork surely can own product's properties so it must gladly have a passage from any CreativeWork property to Product.
> You can just use both types in the itemtype declaration, for example,
> itemtype="Book Product".
> We're doing this in the #schemabibex group to express offers for a given
> item. And Martin gave a wonderful example of this approach on this list
> just a few days back at
> http://lists.w3.org/Archives/Public/public-vocabs/2013Sep/0206.html

martin hepp
e-business & web science research group
universitaet der bundeswehr muenchen

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Received on Tuesday, 8 October 2013 06:32:29 UTC

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