Re: Indicating main entity / primaryTopic - proposal to use 'schema.org/about' from Jarno van Driel on 2014-05-21 (public-vocabs@w3.org from May 2014)

From: Jarno van Driel <jarnovandriel@gmail.com>
Date: Wed, 21 May 2014 14:04:20 +0200
To: Jocelyn Fournier <jocelyn.fournier@gmail.com>
Cc: Dan Brickley <danbri@google.com>, W3C Web Schemas Task Force <public-vocabs@w3.org>
Message-ID: <CADK2AU1v2wKGUV=pEAcx0RJAaD7nZ123WvJ_nSQvt3+UxVq1vg@mail.gmail.com>
I was wondering, can an entity also have multiple @about properties?

I ask because when chaining multiple entities to a WebPageElement, to me it
seems the following is the logical thing to do:

<body itemscope itemtype="http://schema.org/WebPage">
    ...
    <div itemprop="hasPart" itemscope itemtype="http://schema.org/WPSideBar
">
        <div itemprop="about" itemscope itemtype="
http://schema.org/ContactPoint">...</div>
        <div itemprop="about" itemscope itemtype="http://schema.org/ItemList
">...</div>
    </div>
    ...
</body>

Or would @hasPart or @mentions be prefered over @about?


2014-05-20 23:00 GMT+02:00 Jocelyn Fournier <jocelyn.fournier@gmail.com>:

> Le 20/05/2014 18:16, Dan Brickley a écrit :
>
>  On 20 May 2014 11:28, Jarno van Driel <jarnovandriel@gmail.com> wrote:
>>
>>> Martin, I don't know if I a completely agree about going to the product
>>> forum about this. I think I understand why you might say this, but in my
>>> thread about the working of WebPage (http://bit.ly/1jyFN0g), Jason
>>> Douglas
>>> said:
>>>
>>>  "That said, we probably do need a mechanism for indicating the "primary
>>>> entity" of a webpage when there is one.  Current clients make up their
>>>> own
>>>> heuristics for this, but I think it would be better to have an explicit
>>>> way
>>>> of stating that."
>>>>
>>>
>>> But this is not the main subject of this thread. Maybe a new thread to
>>> discuss the "primary entity" or continuation of the subject in the
>>> thread I
>>> already started is a better place.
>>>
>>
>> This is very much in scope for public-vocabs and for schema.orgdiscussions.
>>
>> There are a few pieces to the puzzle, but the basic idea is simple.
>> Schema.org allows a rich descriptive graph to be embedded in a Web
>> page, which means we often have several entities mentioned; we'd like
>> to know which one is the main one, if any.
>>
>> Consider the second example in http://schema.org/MusicEvent to give us
>> a concrete focus.
>>
>> It describes a 'MusicEvent' (a concert), whose 'location' is a
>> 'Place'. The event lists multiple associated 'offers'; each 'Offer'
>> with price/date etc. info. The event also lists two 'performer's, each
>> a 'MusicGroup'.
>>
>> There is nothing *intrinsically* primary about the event, the
>> location, the offers or the musicians. This description is all the
>> richer because it mentions multiple entities. If I was forced to pick
>> one, I'd probably guess at the MusicEvent being the 'main' entity
>> here, because the others feel slightly more like background
>> information. But there's no need to leave this to guesswork. If this
>> markup was on the homepage of the venue, that publisher might well
>> consider the Place to be the main entity. And if it was on an artist's
>> homepage, they might want to mention the gig (perhaps alongside
>> others) but indicate that the MusicGroup was the main thing.
>>
>> The above sketches this in terms of embedded structured data, but we
>> can also think of this in terms of capturing a very common pattern in
>> Web content. Often Web pages _do_ have a focus on a single entity. If
>> we add a property like mainEntity, it would give sites a way to make
>> this focus explicit.
>>
>> PROPOSAL:
>>
>> 1.
>> We already have "about", "The subject matter of the content.",
>> relating a CreativeWork to a Thing. This is enough to do what we need,
>> if we add clarification and examples.
>>
>> I suggest the description should be updated to  say: "A Thing that is
>> the primary subject matter of this CreativeWork".
>>
>> 2.
>> If we want a more SKOS-like, bibliographic and nuanced notion of
>> 'subject', I suggest we adopt something like Dublin Core's 'subject'
>> to do that work.
>>
>> (DC has "The topic of the resource."/ "Typically, the subject will be
>> represented using keywords, key phrases, or classification codes.
>> Recommended best practice is to use a controlled vocabulary.", from
>> http://purl.org/dc/terms/ )
>>
>> The distinction:
>>
>> if we want to say "This document is about the entity Sweden, i.e. the
>> thing that is sameAs http://en.wikipedia.org/wiki/Sweden
>> http://www.freebase.com/m/0d0vqn), we would use
>> http://schema.org/about   ... i.e. this tells us the main thing that
>> the page is about.
>>
>> but
>>
>> If we want to say, "This document's topic is “environmental impact of
>> the decline of tin mining in Sweden in the 20th century“, we'd be
>> going beyond "about" and would want a more bibliographic subject
>> description, e.g. using DDC or UDC subject classification codes, SKOS
>> etc.
>>
>> (fictional example, I know nothing about tin mining in Sweden)
>>
>> My proposal then is that we break out these two use cases, and target
>> the 'about' more explicitly on the 'main entity' use case.
>>
>> 3. Tweak http://schema.org/mentions
>>
>> We should note that http://schema.org/mentions is a very similar
>> notion to http://schema.org/about except that it allows multiple
>> different entities to be referenced.
>>
>> "Indicates that the CreativeWork contains a reference to, but is not
>> necessarily about a concept."
>>
>> I suggest rewording this in terms of entities/things, since we don't
>> use 'concept' elsewhere:
>>
>> "Indicates that the CreativeWork contains a reference to, but is not
>> necessarily about some particular thing."
>>
>
>
> Hi Dan,
>
> With this description, it's not really easy to make the difference with
> the http://www.schema.org/citation property (not sure BTW I really
> understand the difference :))
>
>
> Thanks,
>   Jocelyn
>
>
>
>> 4. http://schema.org/mainContentOfPage
>>
>> We already have this strange-looking property. It addresses a
>> different use case:
>>
>> it relates a WebPage to a part of that WebPage,
>> "Indicates if this web page element is the main subject of the page."
>>
>> The wording is awkward. It should be something like "Indicates the
>> main element within some Web page." since the expected type is
>> WebPageElement.
>>
>> I'm not convinced that the various types we have under WebPageElement
>> ("A web page element, like a table or an image") really work, but the
>> important point here is that they address a different scenario. A
>> WebPageElement is a piece of markup, like SiteNavigationElement,
>> Table, WPAdBlock, WPFooter, WPHeader, WPSideBar. This is a different
>> idea to the problem of finding the main *entity* that all this markup
>> is describing.
>>
>> HTML already a <main> element, see
>> https://developer.mozilla.org/en-US/docs/Web/HTML/Element/main
>>
>> "The HTML <main> element represents the main content of  the <body> of
>> a document or application. The main content area consists of content
>> that is directly related to, or expands upon the central topic of a
>> document or the central functionality of an application. This content
>> should be unique to the document, excluding any content that is
>> repeated across a set of documents such as sidebars, navigation links,
>> copyright information, site logos, and search forms (unless, of
>> course, the document's main function is as a search form)."
>>
>> I believe most of the use cases for mainContentOfPage are better
>> addressed by <main>.
>>
>> However <main> does not help us pick out a single highlighted entity:
>> the main section of a Web page could still contain microdata/rdfa or
>> json-ld mentioning lots of different entities.
>>
>> It is useful sometimes to know that structured data markup comes from
>> footers or boilerplate rather than the <main> section of a page, and
>> it is probably worth including some examples of this on the schema.org
>> site.
>>
>>
>> 5. Avoiding ratholes
>>
>> If we can please discuss this without slipping into discussion of
>> http://www.w3.org/2001/tag/group/track/issues/14 I'd be happy. There
>> are places in schema.org usage where we tolerate an URL for a WebPage
>> being used in place of an URL that is more explictly for the
>> real-world entity itself. For example in http://schema.org/Person we
>> write "<a href="http://www.xyz.edu/students/alicejones.html"
>> itemprop="colleague">Alice Jones</a>".
>>
>> Clarifying the use of 'about' as above could help such pages clarify
>> which real world entity they are 'about'. This won't solve every issue
>> around entity disambiguation, but it will improve the basic support we
>> have within schema.org for stating such distinctions when we want to.
>>
>> (Sorry this was such a long mail...)
>>
>> Finally, let's also try not to get stuck on syntax issues at this
>> stage. We'll have to find the best patterns in Microdata/RDFa and
>> JSON-LD that we can for this, and it may sometimes be tricky. Here's
>> an attempt at amending the MusicEvent example by adding a WebPage and
>> 'about' - https://gist.github.com/anonymous/cf7e24f6378b176aa010 . We
>> might want to discuss a reverse property that could be expressed on
>> the entity rather than the page, for example.
>>
>> cheers,
>>
>> Dan
>>
>>
>
>
Received on Wednesday, 21 May 2014 12:04:47 UTC