A query algebra for object-oriented databases integrating versions

Presents an algebra to query object-oriented databases that integrate versions. This algebra rests on an object-oriented data model which permits, by means of versions, the description of both value and schema evolutions for entities. The specificities of versions are taken into account. So, versions describing an entity may be queried either by considering the derivation hierarchy they belong to (all the entity states are considered) or independently, one from another (only some entity states are considered)