Re: OA and RDFa (Was: Annotation Serializations)

Hey Paolo,

see below.

On 22 Jan 2014, at 04:48 , Paolo Ciccarese <paolo.ciccarese@gmail.com> wrote:

> Dear Ivan and all,
> I would start from the example Ivan included in a previous email http://lists.w3.org/Archives/Public/public-openannotation/2014Jan/0038.html
> I also copied it to the Wiki http://www.w3.org/community/openannotation/wiki/RDFa were we can collect the results of the discussion.
> 
> Here below a couple of initial considerations/exercises. Ivan I am trying to understand this myself so please chime in and explain where necessary.
> 
> 1) Target
> 
> Current:
> <blockquote property="hasTarget"
>           resource="http://example.com/sourcedoc.html"
>           cite="http://example.com/sourcedoc.html"
>           data-prefix="essential feature of the memex. "
>           data-suffix=" When the user is building a tra" typeof="">
>     <p>The process of tying two items together is the important thing.</p>
>     <footer>
>           - <cite>
>              <a href="http://en.wikipedia.org/wiki/Vannevar_Bush">
>                 <span>Vannevar Bush</span>
>              </a>
>         </cite>
>     </footer>
> </blockquote>
> 
> Using the distiller this becomes:
> ...
> "hasTarget": "http://example.com/sourcedoc.html"
> ...
> 
> and not what I would expected given Doug example:
> "hasTarget": {
>     "@id": "http://example.com/specifictarget/0001", 
>     "@type": "SpecificResource", 
>     "hasSelector": {
>         "@id": "http://example.com/selector/0001", 
>         "@type": "TextQuoteSeletor", 
>         "prefix": "essential feature of the memex. ", 
>         "match": "The process of tying two items together is the important thing.", 
>         "suffix": " When the user is building a tra"
>     }, 
>     "hasSource": "http://example.com/sourcedoc.html"
> },
>         
> Was that intentional? Were you (or Doug) thinking of using 'data-prefix' and 'data-suffix' as shortcuts?

Indeed. As I said back then, I was not not sure what really the intention of Doug was and how it could/should be expressed in OA (ie, how to express the relationship to Bush.), so I skipped over this. There were some separate mails on this since which I did not follow in details, unfortunately, but I guess that is what you use below.

> 
> This is an exercise for a more complete - and more complex! - approach, which allow the user to add the SpecificResource/Selector info if needed (only blockquote here):
> 
> <blockquote property="hasTarget" resource="http://example.com/specifictarget/0001" 
>     typeof="SpecificResource" cite="http://example.com/sourcedoc.html" >
>     <details>
>         <summary>Source</summary>
>         <a property="hasSource" resource="http://example.com/sourcedoc.html" href="http://example.com/sourcedoc.html">http://example.com/sourcedoc.html</a>
>     </details>
>     <div property="hasSelector" resource="http://example.com/selector/0001" typeof="TextQuoteSeletor">
>         <p property="prefix" style="display: none;">essential feature of the memex. </p>
>         <p property="exact">The process of tying two items together is the important thing.</p>
>         <p property="suffix" style="display: none;"> When the user is building a tra</p>
>     <div>      
>     <footer>
>       - <cite>
>              <a href="http://en.wikipedia.org/wiki/Vannevar_Bush">
>                 <span>Vannevar Bush</span>
>              </a>
>         </cite>
>     </footer>
> </blockquote>
> 
> I am using 'details' defined as 'The details element represents a disclosure widget from which the user can obtain additional information or controls.' With the idea that the source could be shown/hidden. Probably the 'summary' element can be omitted.
> 
> This markup - that could be simplified - generates the above JSON-LD snippet.
> It is obviously more complicated.

Right. I have made a little bit simpler below, but not much:

       <blockquote property="hasTarget"  
            typeof="SpecificResource" cite="http://example.com/sourcedoc.html" >
            <details>
                <summary>Source</summary>
                <a property="hasSource" resource="http://example.com/sourcedoc.html" href="http://example.com/sourcedoc.html">http://example.com/sourcedoc.html</a>
            </details>
            <div property="hasSelector" typeof="TextQuoteSeletor">
                <meta property="prefix" content="essential feature of the memex.">
                <p property="exact">The process of tying two items together is the important thing.</p>
                <meta property="suffix" content="When the user is building a tra">
            <div>      
            <footer>
              - <cite>
                     <a href="http://en.wikipedia.org/wiki/Vannevar_Bush">
                        <span>Vannevar Bush</span>
                     </a>
                </cite>
            </footer>
        </blockquote>

One of the simplifications is a matter of choice: I would expect blank nodes are perfectly all right for what you referred to as .../001; unless other parts of the system needs explicit URI-s for these, they are perfectly fine as blank nodes imho. 

The other, more important change: when using RDFa, the <meta> and <link> elements are valid everywhere in the document (much as is the case in microdata), and I think that is a much cleaner pattern than using a @style="display:none".

Note that the extra complication here is conceptual and not OA or RDFa specific: it is the stable URI/anchor issue for a quote in another document. That issue, in general, should be part of the WG (although I personally like the approach taken in OA, which is pretty pragmatic...)


> 
> 2) Embedded textual body
> 
> Current:
> <p property="hasBody" typeof=""><span property="rdf:value">Annotations are at the Web's core.</span></p>
> 
> According to specs - and forgetting dc:format for now - that should be something like:
> <p property="hasBody" typeof="cnt:ContentAsText"><span property="cnt:chars" >Annotations are at the Web's core.</span></p>
> or, assuming to have a RDFS aware processor (as the domain of cnt:chars is cnt:ContentAsText), just:
> <p property="hasBody" typeof=""><span property="cnt:chars">Annotations are at the Web's core.</span></p>
> 
> The above would generate something on the lines of:
> hasBody": {
>     "@type": "cnt:ContentAsText",  
>     "cnt:chars": "Annotations are at the Web's core."
> },
> 
> Again, at this stage, these are incomplete exercises for discussion purposes.
> Comments are more than welcome.
> 

Yes, that is correct.

Unfortunately (see on the wiki) the @prefix="cnt: http://...." is necessary in this case, which makes it a bit more complex because namespace have to be defined. This is not the case for foaf, because that is part of RDFa's initial context, as a widely used vocabulary, and therefore it can be used without declaration. I wonder whether there are no alternatives to 'cnt' that would make this simpler.

(The RDFa WG shied away from the definition of a @context of the same power as in JSON-LD. We had it defined, there were actually implementations for it at the time, but the issue of 'what happens if the context is not available' became a stumbling block, because it would have made the output of the RDFa processing unusable. JSON-LD was probably less shy on this but, also, I guess what prevailed was that the JSON content still made some sense, so an unreachable @context may not have been such a problem. I personally think it is a pity, but, well, that is the way it is...)

Thanks!

Ivan


> Paolo
> 
> 


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