Does Chronus support temporal joins?
Yes – Chronus has extensive support for temporal joins. Relationally joining multiple tables involves generating a subset of the Cartesian product of all tuples in the tables. In a SQL query, this subset is determined by the columns specified in the SELECT clause and by the predicates in the WHERE clause. In a temporal join, it is further restricted by temporal predicates. However, a temporal join differs from a non-temporal one because the temporal attributes in the operand tables must be treated specially. To perform temporally valid joins, we must combine the temporal information from the operand tables and generate a single meaningful temporal column. The valid-time component in each temporal table must be well-defined before performing such joins. If all temporal information and queries concerned past events, capturing the semantics of the information would not be difficult. However, temporal databases must also describe events that are ongoing, and may also need to describe futur
