- From: Niklas Lindström <lindstream@gmail.com>
- Date: Sun, 9 Mar 2014 14:19:44 +0100
- To: Jarno van Driel <jarnovandriel@gmail.com>
- Cc: Gregg Kellogg <gregg@greggkellogg.net>, public-rdfa <public-rdfa@w3.org>
- Message-ID: <CADjV5jfQLRpgEb2ZabRLh2M_kUnzp-JCw20D6b+7Jq_=jGGSzw@mail.gmail.com>
Hi Jarno and Gregg!
It seems to me that this is a good example of where @itemref-like
functionality is quite unnecessary in RDFa. The #copyright-holder simply
contains a link from the page to the corporation, and the #publisher-url
and #publisher-description contain properties of that corporation. The
resulting microdata, however, outputs two different nodes for what
seemingly is the same corporation, so perhaps the example has been
simplified too much, thus obscuring what is actually needed?
Still, In RDFa, instead of adding different @id:s to disparate parts of the
page which are about the same resource (and then listing them in @itemref),
you simply use @resource to capture the fact that a given block is about it.
Your example can thus be written like this in RDFa Lite:
- - - 8< - - -
<body vocab="http://schema.org/" typeof="ItemPage" resource="#page">
<article property="text">
<div typeof="Article">
<link property="publisher" resource="#corp">
<h1 property="name">How to copy properties in RDFa Lite &
Microdata</h1>
</div>
</article>
<footer property="mentions" typeof="WPFooter">
<div property="text">
<p resource="#page">
<span property="copyrightHolder" typeof="Corporation"
resource="#corp">
<a property="url" href="http://www.example.org">
<span property="name">Corporation name</span>
</a>
<span property="description">Corporation description</span>
</span>
</p>
</div>
</footer>
</body>
- - - >8 - - -
In my opinion, this is a more convenient way of handling data smeared out
in a messy tag soup (with the results being shorter and more legible). Of
course, you need to name these resources, unless they already have formal
URIs, but that's easily done with a fragment identifier or a bnode id. (And
note that in microdata, you instead need to ensure that a layout designer
doesn't meddle with the @id values used by @itemref, for quite different
reasons (their use in CSS and JS).)
Also, the resulting data here doesn't contain two distinct nodes for what
is apparently meant to be the same corporation.
Remember, it is only when you need to duplicate a set of properties for
different resources that rdfa:copy is necessary. And even in those
circumstances, you might be able to leverage the way @resource can group
descriptions together, to build up one pattern from disparate parts of the
page.
I'd be happy to take a look at such examples as well.
Cheers,
Niklas
On Sun, Mar 9, 2014 at 11:51 AM, Jarno van Driel <jarnovandriel@gmail.com>wrote:
> I think your and my latest example just passed each other Gregg. I guess I
> posted mine when you were writing yours because when I compare the two I
> see we implemented the same workaround by means of additional @resource.
>
> "I wouldn't recommend the use of included patterns in RDFa, but it can be
> made to work."
> I wouldn't recommend it either but unfortunately the everyday website out
> there consists out of a HTML-soup which doesn't allow for Semantic markup
> to be added in a nice and clean way. Now I mainly work on already existing
> websites, where I have to make do with HTML that's already in place.
> Therefore itemref or rdfa:pattern are indispensable when organizing/linking
> data that's smeared out over many different HTML elements on a page. I am
> very aware this results in markup that isn't 'nice' but it helps create
> meaning even if the HTML is a mess.
>
> "P.S., I think it's great that you're trying to describe this for a wider
> audience!"
> Well, I'm not doing it alone. Aaron Bradley is acting as the devil's
> advocate by asking me questions which mess up the solutions I provide.
> Which in return forces me to come up with different solutions and ask a lot
> of questions at the public-vocabs (and now here as well). :)
>
> So trying to do something for a bigger audience will most definitely end
> up in something that has been contributed by many people. As always this
> kind of stuff ends up being a multi-community/person effort since it brings
> together so many different specializations and specifications.
>
> --
>
> Andy and Gregg,
> Thanks for sharing your knowledge, I'll make sure re-share it and am
> hopeful it will result in an article (or series of) which will try to serve
> anybody who is (or should be) interested in this type of info.
>
>
> 2014-03-09 6:46 GMT+01:00 Gregg Kellogg <gregg@greggkellogg.net>:
>
> On Mar 8, 2014, at 5:50 PM, Jarno van Driel <jarnovandriel@gmail.com>
>> wrote:
>>
>> "..the @resource attributes get in the way.."
>> Could you explain this to me a bit more please Gregg? Because if I parse
>> my last markup through the Structured data linter and RDFa Play I get 100%
>> the same outcome as with your markup. Yandex and Google see the same data
>> as well (in a ever so slightly different manner).
>>
>> When I look at the output these parsers have no trouble extracting the
>> @resources as different rdfanodes. Unless I'm completely overlooking
>> something, or am breaking some cardinal rules, which both are feasible
>> since I just got around to looking more deeply into RDFa Lite.
>>
>>
>> In order to be able to reference the publisher-uri and
>> publisher-description information as patterns, they need to have an
>> identifier, which I supplied by adding @resource (and
>> @typeof="rdfa:Pattern) to each. However, this changes the scope of their
>> properties relative to the copyright-holder.
>>
>> In you're RDFa version you weren't able to access the publisher-uri or
>> publisher-description, as you do from Microdata. The RDFa property copying
>> uses a resource of type rdfa:Pattern, which must be identified as a
>> resource. For this reason, I added the @resource and @typeof for both the
>> publisher-description and publisher-url. However, doing that, changes the
>> current subject for each of these, so the "url" and "description"
>> properties are allocated to different resources. To get around this, I
>> added the rdfa:copy properties both the the publisher reference, and to the
>> copyright-holder, so that the properties appear in each of them. I wouldn't
>> recommend the use of included patterns in RDFa, but it can be made to work.
>>
>> I'd recommend both for Microdata and RDFa to keep references simple, and
>> using included references, while possible, can make things more confusing.
>> This is certainly not a pattern we were concerned about when crafting the
>> property copying mechanism in HTML+RDFa. They two really work quite
>> differently: Microdata requires full access to the DOM so that referenced
>> elements can be copied, which requires random access to the DOM. The RDFa
>> mechanism operates at a semantic level, by creating triples as normal. RDFa
>> is intended to work with streaming processors, where there is no
>> random-access to the DOM. The spec provides details of the rules which are
>> applied to achieve the effect of property copying [1], but it's not really
>> magic to RDFa, and could just as easily be done for triples extracted from
>> Turtle, or even Microdata, if the appropriate copying rules were applied.
>>
>> I understood that you didn't know how to deal with a pattern embedded in
>> another pattern, which I attempted to address for you. I think that the
>> RDFa I provided does essentially what your Microdata does. If you want to
>> discuss more, we should probably meet on IRC.
>>
>> Gregg
>>
>> P.S., I think it's great that you're trying to describe this for a wider
>> audience!
>>
>> [1] http://www.w3.org/TR/rdfa-in-html/#implementing-property-copying
>>
>>
>> 2014-03-09 1:33 GMT+01:00 Gregg Kellogg <gregg@greggkellogg.net>:
>>
>>> Hi Jarno, I don't think you can do precicely what you want, since if a
>>> pattern is included in another pattern, the @resource attributes get in the
>>> way. You can do it by adding some more rdfa:copy properties. This is what I
>>> came up with:
>>>
>>> <body vocab="http://schema.org/" resource="#item-page"
>>> typeof="ItemPage">
>>> <link property="rdfa:copy" href="#copyright-holder">
>>>
>>> <article property="text">
>>> <div resource="#article" typeof="Article">
>>> <div property="publisher" typeof="Corporation">
>>> <link property="rdfa:copy" href="#publisher-url"/>
>>> <link property="rdfa:copy" href="#publisher-description"/>
>>> </div>
>>>
>>>
>>> <h1 property="Name">How to copy properties in RDFa Lite &
>>> Microdata</h1>
>>> </div>
>>> </article>
>>>
>>> <footer property="mentions" typeof="WPFooter">
>>> <div property="text">
>>> <p resource="#copyright-holder" typeof="rdfa:Pattern">
>>> <span property="copyrightHolder" typeof="Corporation">
>>> <link property="rdfa:copy" href="#publisher-url"/>
>>> <link property="rdfa:copy" href="#publisher-description"/>
>>> <span resource="#publisher-url" typeof="rdfa:Pattern">
>>> <a id="publisher-url" property="url" href="
>>> http://www.example.org" title>
>>> <span property="name">Corporation name</span>
>>> </a>
>>> </span>
>>>
>>> <span resource="#publisher-description" typeof="rdfa:Pattern">
>>> <span id="publisher-description"
>>> property="description">Corporation description</span>
>>> </span>
>>> </span>
>>> </p>
>>> </div>
>>> </footer>
>>> </body>
>>>
>>> Gregg Kellogg
>>> gregg@greggkellogg.net
>>>
>>> On Mar 8, 2014, at 2:37 PM, Jarno van Driel <jarnovandriel@gmail.com>
>>> wrote:
>>>
>>> <body vocab="http://schema.org/" resource="#item-page"
>>> typeof="ItemPage">
>>> <link property="rdfa:copy" href="#copyright-holder">
>>>
>>> <article property="text">
>>> <div resource="#article" typeof="Article">
>>> <link property="publisher" typeof="Corporation" href=?????>
>>>
>>> <h1 property="Name">How to copy properties in RDFa Lite &
>>> Microdata</h1>
>>> </div>
>>> </article>
>>>
>>> <footer property="mentions" typeof="WPFooter">
>>> <div property="text">
>>> <p resource="#copyright-holder" typeof="rdfa:Pattern">
>>> <span property="copyrightHolder" typeof="Corporation">
>>> <a id="publisher-url" property="url" href="http://www.example.org"
>>> title>
>>> <span property="name">Corporation name</span>
>>> </a>
>>>
>>> <span id="publisher-description" property="description">Corporation
>>> description</span>
>>> </span>
>>> </p>
>>> </div>
>>> </footer>
>>> </body>
>>>
>>>
>>>
>>
>>
>
Received on Sunday, 9 March 2014 13:20:43 UTC