AnnoSys (https://annosys.bgbm.org/) implements an online annotation system for networked and highly structured biodiversity data. It is tailored as a sustainable data quality tool to correct biodiversity data and allows specialists to enrich data in publicly available data portals. For that, it supports the creation of and search for annotations referring to digital specimen and occurrence data representations using community-specific criteria, such as scientific name, identification, nomenclatural type, and collection.

Within its first project phase, AnnoSys developed workflows and methods supporting online annotations of collection metadata. Its current publicly available release version integrates a dozen biodiversity data portals providing collection and observation data in the botanical and zoological domain published in GBIF/BioCASE networks via the Biological Collection Access Service (BioCASe). The data portal integration includes the display of available annotations for a given collection data object as well as redirecting data portal users to AnnoSys' desktop-oriented web interface providing a comfortable means to edit, manage and publish further annotations. Additionally, the web interface enables curators (on request) to communicate and justify decisions with regard to the acceptance or rejections of annotations referring to data objects of their collections. A subscription-based message system permits registered AnnoSys system users to receive an email about a self-defined subset of annotation processing events, e.g. specific taxon names, countries, collections, or institutions.

The AnnoSys repository archives annotations and the related original collection data and are publicly retrievable and integrable with other systems through Linked Data, REST (REpresentational State Transfer) and SPARQL-based web services. It is based on a generic data model that can be adapted to a variety of application domains and XML-standards besides ABCD and uses the W3C Open Annotation Data Model to store and exchange annotation data, hence making it highly interoperable and flexible.