Mapping methods and query for aggregation and association in object-relational database using collection

Association and aggregation are two relationship types in the object-oriented conceptual model (OOCM) that frequently involve collection of elements/attributes. However, very often when the relationships are stored in object relational database (ORDB) the collection is flattened like it is implemented by pure relational model. In this paper we propose the mapping methods to preserve the collection semantics in ORDB using collection data type. In aggregation we propose methods for different constraints types, while in association we propose methods for "many" cardinality (I:N, N:N) relationships. In addition, we also show how queries can be performed in the relationships using collection type.