Month: August 2009

Understanding Microdata, now with more understanding

Okay, I’m giving this whole HTML5 microdata a shot for real. 4475 HTML pages of it in fact.

After reading what Hixie wrote, tried creating a new sample. Didn’t feel any stranger then the markup for RDFa. From a typing perspective, it is annoying to have to type the whole URI, from a reading perspective it’s much clearer what’s going on, at least to me. I also won’t be typing these every time, template systems are neat like that. Now as far as I can tell the XHTMLy solution to this using XML entities is not supported in HTML5.

Should have known better then to jump right from the sample into doing template markup. Having spent the morning making sure that I was producing valid HTML5, the addition of microdata caused errors at Validator.nu. It seems the method of using <link> elements is not currently supported by the validator. In fact even our sample fails to validate. Ugh.

Philip’s parser works nicely for testing to see if what I have is working, given that I can’t use the validator.

At this point I have markup for the relationships of Manifestations of an edition (Expression). Adding the markup for the publication dates was much more unpleasant. It seems that I have to repeat the whole:

<some_tag
     itemprop="http://vocab.org/frbr/core#embodiment"
     item="http://purl.org/vocab/frbr/core#Manifestation">
     <link itemprop="about" href="${product.subject}">

every time I need to talk about ${product.subject}. And the microdata parser happily adds the relationship all over again.

  <http://vocab.org/frbr/core#embodiment> <urn:x-domain:oreilly.com:product:9780596007683.BOOK> ;
  <http://vocab.org/frbr/core#embodiment> <urn:x-domain:oreilly.com:product:9780596806316.BOOK> ;
  <http://vocab.org/frbr/core#embodiment> <urn:x-domain:oreilly.com:product:9780596802189.EBOOK> ;
  <http://vocab.org/frbr/core#embodiment> <urn:x-domain:oreilly.com:product:9780596802028.SAF> ;
  <http://vocab.org/frbr/core#embodiment> <urn:x-domain:oreilly.com:product:9780596007683.BOOK> ;
  <http://vocab.org/frbr/core#embodiment> <urn:x-domain:oreilly.com:product:9780596806316.BOOK> ;
  <http://vocab.org/frbr/core#embodiment> <urn:x-domain:oreilly.com:product:9780596802189.EBOOK> .
    .

There is a great deal of markup smell coming from this page now. I think from here I’m going to try this as XHTML (5?) and go back to RDFa and see how that goes.

Will send this and earlier post to WhatWG mailing list as soon as my subscription to the WhatWG mailing list is approved.

Trying to understand Microdata? RDFa?

Been trying to follow the RDFa, microdata messwork. This isn’t academic. I have a nice open ticket that says “Insert inline metadata into O’Reilly Catalog pages” which is due in a large release at the end of September.

Do I expect Google to index my page a whole lot better? Nah. (That’s why we’re doing complete HTML chapters of our books, and full HTML Table of Contents). Do I expect our internal tools to index it better? Maybe, if I pray to the right search gods. Can I think of some some crazy shit to do in jQuery with the few attributes I have in there? Oh yes. What exactly is going to come of us putting micodata in our pages? No clue, but then we didn’t really know what Web 2.0 was in 2004, or this strangeWorld Wide Web ( Online Whole Internet Catalog, in which we uh, printed the internet) thing was in 1992.

Lets get started. I know what metadata I need to express. Here is a short version of it expressed in Turtle. There are a number of other fields, but this will give you the gist.

@prefix dc: <http://purl.org/dc/terms/> .
@prefix frbr: <http://purl.org/vocab/frbr/core#> .

<http://purl.oreilly.com/works/45U8QJGZSQKDH8N> a frbr:Work ;
     dc:creator "Wil Wheaton"@en ;
     dc:title "Just a Geek"@en ;
     frbr:realization <http://purl.oreilly.com/products/9780596007683.BOOK>,
         <http://purl.oreilly.com/products/9780596802189.EBOOK> . 

<http://purl.oreilly.com/products/9780596007683.BOOK> a frbr:Expression ;
     dc:type <http://purl.oreilly.com/product-types/BOOK> . 

<http://purl.oreilly.com/products/9780596802189.EBOOK> a frbr:Expression ;
     dc:type <http://purl.oreilly.com/product-types/EBOOK> .

This sample uses two vocabularies that exist in the wild. Dublin Core, which is a very mature standard developed by a reasonably heavy weight process with many serializations, and uses. FRBR too is a standard developed by a rather austere body the International Federation of Library Associations and Institutions the RDF realization of it however isn’t from them but rather a few guys who needed to represent it. Reasonably smart few guys, but no giant standards body here.

Took about 15 minutes to whip up a simple RDFa based representation. Now, I know RDF reasonably well, XML very well, and have decent HTML skills. So I admit my experience is not going to be the norm, but it didn’t feel a whole lot harder then the first time I was trying to use hCard. I screwed up a few times, mixing up where to use rel= vs. property=. I also forgot that I can’t just stick a <UL> in another <UL>, need the picky <LI>, also left off at least one close tag. Made all those mistakes in just 32 lines of HTML. But a few quick iterations with validation and it was all green check boxes. I screwed up my late night hand written HTML at about the same rate I screwed up RDFa attributes. I had read the RDFa primer two months ago, but didn’t remember much other then there were some attributes and they went on some tags. Didn’t use the primer, just looked at the example content from RDFa4Google. Used Elias Torres RDFa parser to test my results and validator.w3.org for my HTML.

Felt reasonably happy with my RDFa result. Worked as expected. Microdata time!

Okay, got my Microdata spec. Finding a validator or parser however did not go well. 5 minutes in Google and Bing, turned up the expected HTML5 validator.nu but nothing in the way of a microdata validator or parser. I’ll be honest I was very tempted to stop here. Given the mistakes I made with RDFa, I’m very skeptical of my ability to write Microdata without the help of a parser. But I imagine there is one, and once I post this someone will tweet about it 5 minutes later.

Huh, okay, I have my outer item for the Work:

<div id="http://purl.oreilly.com/works/45U8QJGZSQKDH8N" 
                item="http://purl.org/vocab/frbr/core#Work">
    <ul>
        <li><label>Title:</label>
          <span itemprop="http://purl.org/dc/terms/title">
            Just a Geek</span></li>
        <li><label>By</label>
          <span itemprop="http://purl.org/dc/terms/creator">
            Wil Wheaton</span></li>

That wasn’t very hard at all. I’m completely lost at how to relate that work to the two expressions however. It looks like I’m limited to my microdata being in an <a> tag link to the expressions. And I really don’t understand the idea behind:

The value is the element’s textContent.

Does this mean I can’t use any data that isn’t displayed directly on the page? If the data would be better expressed in a machine readable form? In my case product type http://purl.oreilly.com/product-types/EBOOK really isn’t very human friendly. Ideas on how to express the same metadata or equivalent in microdata are very welcome. This is the best I could do.

I was expecting more tooling and examples from Microdata given it’s inclusion in HTML5. I was very surprised by the lack of tooling and almost complete lack real world examples.