If you annotate text, you frequently want to attach information to (word or character position) intervals. And you do complex queries over these interval annot

If you annotate text, you frequently want to attach information to (word or character position) intervals. And you do complex queries over these interval annotations, e.g. (for a simple example) "which sentences contain both a date and a room number". Because of the scale of corpora, people often do the storage and queries over SQL databases rather than in-memory, but the principle is the same.