Each BEL Statement can optionally be annotated to express knowledge about the statement itself. Some important uses of annotations are to specify information about the:
- biological system in which the observation represented by the statement was made
- experimental methods used to demonstrate the observation
- knowledge source on which the statement is based, such as the citation and specific text supporting the statement
Examples of annotations that could be associated with a BEL Statement are the:
- PubMed ID specifying the publication in which the observation was reported,
- Species, tissue, and cellular location in which the observations were made, and
- Dosage, exposure and recovery time associated with the observation.