An object-oriented system for managing relational numerical data includes a relation interface that provides access to a relation and its attributes and tuples, where an attribute is a data item with a numeric value and a relation is a set of n-tuples of attribute values, where the relation interface maintains its tuples in a fixed order and is adapted to selecting subsets of attributes and/or tuples where a new relation interface instance is created, an iterator interface for iterating over the tuples of a relation, where the iterator is adapted to acquiring the tuple attribute data as data is being accessed, and a notification interface for notifying other classes whenever changes occur in a relation interface instance.