Implement RDFa output of all public codings in live content

[danohu]

[PHP] For semantic web integration of Open Ethnographer.

[danohu]

The architectural issue here is that annotator uses javascript/json, adding annotations after the page has loaded. But for RDFa to be useful, it should be accessible to scrapers and other stupid clients -- which basically requires including it in the HTML.

I'd appreciate advice/comments here -- I have little experience with RDFa. I see the following options, in order of increasing effort required:

• just add the RDFa in javascript, meaning that only browser-based (or browser-imitating) clients can use it
• use json-ld instead of RDFa. This lets us keep the existing annotator js architecture, just add some functions to generate linked-data
• generate HTML with the RDFa included. This is the ideal from the RDFa perspective, but seemingly requires us to duplicate or replace much of what annotatorjs is doing.

Do we have a use case for RDFa? That might help clarify what we need to implement, and how much work it is worth putting into this.

[tanius]

The most frequent use case of the linked data would be to use Open Ethnographer to import and / or query content and ethnographic tags from a third-party website. Until starting this importing and querying feature, publishing the linked data is just a gesture of goodwill towards the linked data crowd, with not much real-world use expected. So we could keep this issue open until also adding the handling of third-party linked data.

I originally thought that your third alternative would be the way to go, adding in the markup on the fly via a corresponding Drupal text filter hook. The main advantage of RDFa is that it conforms to linked data output format in the rest of Drupal Core.

However, I also found that the Open Annotation spec fits our needs better (see the Software Design under "Coding syntax for presentation"). The advantage from an implementation perspective is that Open Annotation uses stand-off annotation, so we can publish the annotations in a separate linked data file. (The disadvantage is that Open Annotation is not in widespread use. But Open Ethnographer instances will be its own main linked data consumers anyway.)

Result: If we have time for the 1.0 release, we can include this linked data rendering feature in an economical way, and that could be a separate RDF file with Open Annotation data.