A generalised temporal algebra

The algebra (TNA) of a generalised temporal database model supporting temporal relations nested to any finite depth is presented. The temporal nested relations consist of temporal nested attributes which are formed from temporal attributes together with the corresponding time-varying attributes. Therefore, the temporal dimension of the model is nested and is not integral with the corresponding time-dependent value. All the operations of the algebra are defined recursively and are proved to be closed. In particular, considering the natural join operation for temporal nested relations, different cases are presented, distinguished by the types and the nesting levels of the common attributes that participate in the natural join operation.