Assign concepts to notes
Have a mechanism to assign keywords/concepts to articles and to notes.
Two approaches 1) URL, 2) free-text
Some articles might want to use terms from a controlled vocabulary e.g., ACM uses CCS.
Blog posts might want free-text or an URL.
+1

Part implementation: the bookmarking (annotation) lets the user use free-text (separated by comma) to tag.
The approach for URLs would use the oa:classifying motivation with some access to a controlled vocabulary from generic (e.g., DBpedia, WordNet) to domain specific - this might make sense to have out of the box. In cases of bottom-up marking. The domain specific dictionaries/taxonomies can be left as extensions.. the UI around that might do stuff like autocompleting and what not.