Annotation grouping mechanism?

Dear list,


as part of my work on the Annotorious [1] image annotation library, there was recently discussion about a grouping mechanism for image annotations. I was wondering whether there are any thoughts about how to best model annotation groups in WebAnno.


From the users' point of view, they'd simply expect something familiar, like you have in your average shape drawing tool (Powerpoint, Inkscape, Illustrator et al.): you'd draw your shape selections on the image; then select multiple shapes (by dragging a box around them, SHIFT+clicking, etc.); and then you group them via keyboard shortcut, right-click menu, whatever.


I wonder if there's a position on best practices for expressing such an association in a WebAnno-compliant way. Should this best be treated as a single annotation, with multiple targets? (Or a single "multi-polygon" SVG selector?) What if users need to maintain the association between particular annotation bodies and a particular target shape? (I.e. what if this needs to be modeled as multiple annotations.)


Or is this outside of the scope of the spec, and implementations should handle this via their own (proprietary) grouping mechanism? E.g. by as assigning "group IDs" in a dedicated annotation body? (Perhaps with "purpose = grouping"?)


Any thoughts appreciated!


Cheers,

Rainer


[1] https://recogito.github.io/annotorious