Since the Science Archive is based on an object-oriented database, we have classes for each object, not tables as opposed to objects in a relational database. The classes are linked to each other either by inheritance or by association .
Inheritance is a way to specialize a class.
Every data member of the base class is also member of the inherited class, but the inherited class may have additional data members. In the schemata below, inheritance is represented by a large empty arrowhead between the classes. Associations link classes to one another. Photometric Survey Objects Objects of the photometric survey are all members of the base class PhotoObj . A secondary object may be associated to more than one primary if the secondary observation is of a bad quality and could not be resolved into two or more objects.