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working of schema.org/WebPage

From: Jarno van Driel <jarno@quantumspork.nl>
Date: Thu, 17 Apr 2014 19:40:14 +0200
Message-ID: <CAFQgrbY7iGpBLN-3kfL7w=UR6TLOeKTWJ4_8KncRgsVuyE2M4w@mail.gmail.com>
To: Public Vocabs <public-vocabs@w3.org>
I'm trying to understand semantic mechanisms better but am a bit confused
about schema.org/WebPage and I'd like to know how it works.

Now it could well be I understand certain terminologies wrong, so please
bare with me and be so nice to correct me when needed.

1] The description of http://schema.org/WebPage says:
"Every web page is implicitly assumed to be declared to be of type WebPage,
so the various properties about that webpage, such as breadcrumb may be
used. We recommend explicit declaration if these properties are specified,
but if they are found outside of an itemscope, they will be assumed to be
about the page."

code example:
<body itemscope itemtype="http://schema.org/WebPage">
  <!-- Content -->
</body>

Now if the WebPage is the only entity is it then considered to be the
'Subject', the 'Object' or both?

2] If the WebPage contains an entity, let's say a Product, without
specifying a property on the Product and I check this with Google's SDTT, I
see 2 'root' entities, since there is no property to chain the two
together. Yet I get the impression the Product gets treated as the
'Object', since it's the Product that gets used for Rich snippet
extraction, and that therefore the WebPage is the 'Subject' :

code example:
<body itemscope itemtype="http://schema.org/WebPage">
  <span itemprop="name">Page title</span>

  <div itemscope itemtype="http://schema.org/Product">
    <span itemprop="name">Product name</span>
    <!-- Product properties -->
  </div>
</body>

Now since "Every web page is implicitly assumed to be declared to be of
type WebPage" I was wondering if there also is a property that is
'implicitly assumed to be declared' (something like @contains) on the first
entity that comes after it, like Product in this case, which indicates that
the Product is the 'Object'?

And if not, than how does a parser 'know' which of the entities is the
'Subject' and which is the 'Object', shouldn't there be a predicate for
this?

3] When a WebPage contains a bunch of 'root' entities, how does a parser
make sense of this, does the DOM have anything to do with this?

<body itemscope itemtype="http://schema.org/WebPage">
  <span itemprop="name">Page title</span>

  <div itemscope itemtype="http://schema.org/Product">
    <span itemprop="name">Product 1 name</span>
    <!-- Product properties -->
  </div>

  <div itemscope itemtype="http://schema.org/Product">
    <span itemprop="name">Product 2 name</span>
    <!-- Product properties -->
  </div>

  <div itemscope itemtype="http://schema.org/LocalBusiness">
    <span itemprop="name">Business name</span>
    <!-- Product properties -->
  </div>
</body>

Now the above could be full of misunderstandings because I lack in
theoretical knowledge still, but that's exactly the thing I'm hoping to
change. Who can enlighten me?
Received on Thursday, 17 April 2014 17:40:42 UTC

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