One of the most important tasks of genome projects is the interpretation of experimental data in order to derive biological knowledge from the data. To achieve this goal, researchers typically search external data sources, execute analysis programs on the biosequences, analyze previous annotations and add new annotations to register their interpretation of the data. This paper first elicits the functional requirements of biosequence annotation systems. Then, it describes BioNotes, a tool that meets these requirements, stressing the advantages it brings to the researchers in this area.