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RE: Inverse Properties in Microdata:, was Re: schema.org update, v1.8: added WebSite type; broadened isPartOf to relate CreativeWorks

From: Markus Lanthaler <markus.lanthaler@gmx.net>
Date: Tue, 5 Aug 2014 12:04:09 +0200
To: "'W3C Web Schemas Task Force'" <public-vocabs@w3.org>
Message-ID: <09dd01cfb094$9a9ef1f0$cfdcd5d0$@gmx.net>
On Tuesday, August 05, 2014 12:52 AM, Jarno van Driel wrote:
>> "Why can't we simply recommend people to use RDFa for such
>> "advanced" use cases? Do we want to evolve both formats in the
>> future?"
> I'm not for that at all. It's easy to say "just use RDFa (or JSON-LD)"
> for this, but that doesn't imply:
> a] That person understands RDFa already.

So? They won't understand reverse properties either. Microdata is mostly about trees. Introducing reverse properties doesn't fit very well into that model IMHO.

> Personally I tried RDFa six years ago, failed miserably and turned to
> microdata.

That's a very good point.. at least it was six years ago. A lot of things changed in the meantime. RDFa 1.1 (Lite) is *much* simpler than previous versions. Moving from Microdata to RDFa 1.1 can, in most cases, be done by simply replacing some attribute names. Since I believe a lot of people on this list share your experience, let me quickly summarize the differences looking at all attributes Microdata defines and see how the map to RDFa 1.1:

  itemscope --> vocab="http://schema.org/"
  itemid --> resource
  itemtype --> typeof
  itemprop --> property / rel
  itemref  --> property="rdfa:copy"

Strictly speaking itemscope and vocab serve two different purposes but if you transform Microdata to RDFa the replacement does the job. RDFa doesn't infer the vocabulary from the type that is being used (itemtype in Microdata) but requires it to be explicitly specified (vocab).

> Which was easier to understand when starting out. And by
> now, I've 'sort of' got my head wrapped around it and am stumbling
> back into RDFa because of it, together with the ton of mistakes that
> come with it. But more importantly, it's costing me bucketloads of my
> free time to learn it all. Something I don't think can nor should be
> expected from everybody.

Reading my mini tutorial above, do you still think it will cost you "bucketloads of [your] free time"? Btw. there's a little playground at http://rdfa.info/play/ that visualizes the extracted graph (at least in Chrome and FF)

> If somebody started out learning microdata and has the audacity to
> become any good at it, then that person shouldn't have to discover
> that they need learn a different syntax to be able to take the extra
> step when of running into one of those 1 in a 1000 situations. I think
> that's too much to ask. Especially if adding one attribute to
> microdata can resolve it

Fair enough. But I fear it's actually not that trivial... How are reverse properties, e.g., supposed to be integrated into application/microdata+json: http://www.w3.org/TR/microdata/#json

> b] Website(s) being worked on can not "simply" be rewritten to
> accommodate RDFa.

Are you still sure about that?

>> "Reverse properties are not exactly the simplest thing as this thread has shown."
> Nope, there not 'easy'. And sure, I've asked plenty of questions and
> unfortunately I ask for a lot of input of the folks here, but that's
> because there are so little resources available to learn this type of
> stuff.

Yeah, but we can change that together. And "newcomers" that struggle with this stuff are almost always in the best position to write such material as they do experience these problems themselves. As paradox it sounds, but it is very difficult for experts to write good tutorials for complete newbies. Did you, e.g., write down what you've learned over the years? :-)

> Especially for the everyday developer who is looking for info
> that goes beyond examples on schema.org or any of the sponsor's sites.
> And as long as that info isn't abundantly available it will stay too
> complex for most. Maybe the focus therefore should be more on
> educating folks as opposed to deciding something is too complex before
> ever giving them a chance to properly learn it.

We need to work together to make this happen. Writing and implementing specs is already time consuming enough. I personally, e.g., do that entirely in my free time. No one is paying me or supporting me in any other way to do this. I'm sure a lot other people are in the same situation. So, help in the form of writing simple tutorials and blog posts etc. would be much appreciated :-P

[1] http://www.w3.org/TR/microdata/
[2] http://www.w3.org/TR/rdfa-core/

Markus Lanthaler
Received on Tuesday, 5 August 2014 10:04:43 UTC

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