Supporting annotations on relations

Annotations play a key role in understanding and curating databases. Annotations may represent comments, descrip-tions, lineage information, among several others. Annota-tion management is a vital mechanism for sharing knowl-edge and building an interactive and collaborative environ-ment among database users and scientists. What makes it challenging is that annotations can be attached to database entities at various granularities, e.g., at the table, tuple, col-umn, cell levels, or more generally, to any subset of cells that results from a select statement. Therefore, simple comment fields in tuples would not work because of the combinato-rial nature of the annotations. In this paper, we present extensions to current database management systems to sup-port annotations. We propose storage schemes to efficiently store annotations at multiple granularities, i.e., at the ta-ble, tuple, column, and cell levels. Compared to storing the annotations with the individual cells, the proposed schemes achieve more than an order-of-magnitude reduction in stor-age and up to 70 % saving in the query execution time. We define types of annotations that inherit different behaviors. Through these types, users can specify, for example, whether or not an annotation is continuously applied over newly in-serted data and whether or not an annotation is archived when the base data is modified. These annotation types raise several storage and processing challenges that are ad-dressed in the paper. We propose declarative ways to add, archive, query, and propagate annotations. The proposed mechanisms are realized through extensions to the stan-dard SQL. We implemented the proposed functionalities in-side PostgreSQL with an easy to use Excel-based front-end graphical interface. 1.