Categories associated with an image: define groups

[hamishr]

I would like to be able to associate categories in groups.

If I have an image of a spider eating a fly, I would normally link 3 categories: the name of the spider, the name of the fly and that this is a predator-prey interaction. However, more than that, I want to be able to link 'predator' to the spider and 'prey' to the fly so that later I can extract all spiders attacking prey or all flies being eaten by spiders (you do get cases of flies eating spiders, so one can't make assumptions). So, for the image, I would like to associate one group of categories for the spider's name and its role as predator and another group for the fly's name and its role as prey.

Another example of where this is needed is for a digitized letter: I would like to be able to link the person who wrote the letter as one group (person's name; role: letter writer), the person (or people) who received the letter as another group (person's name, role: letter receiver), and then any number of people who are mentioned in the letter. Admittedly, in this case one is linking to the Category table and the Person table, which makes it more complicated, unless one has a person entry in Categories, which is linked to their entry in People.

[hamishr]

Thinking about this some more, the only way this could work would be if the second category in a group modifies the scope of the first but not the other way round - all seems a bit too complicated. The alternative would be to do away with groups and instead for each category chosen you are able to define a role but again this is likely to be too complicated. The only ways I can think of for doing this in the current Imatch is to (1) have two different copies of the image with different sets of metadata but this gets messy; or (2) have subcategories for the roles (e.g. spiders sp.1, subcategory 'as predator') and then select the subcategory. The second alternative is probably the most elegant. For a person entered as a category, the subcategories could be, e.g. letters written, letters received, mentioned in text, artworks, subject in photograph. I would be interested to know if there are other alternatives.