We argue that representation of temporal relationships (e.g., before, after) is necessary in databases. We propose a graph model for an important class of temporal relationships. This model is shown to be a powerful tool in identifying generic temporal queries, and in describing the process of deduction of temporal relationships. The model provides a framework to estimate the cost of query evaluation and to identify domain characteristics for query optimization. We provide an outline of

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... query processing to illustrate how domain properties may be utilized. We conclude by presenting an interesting computational model for the temporal domain that trades completeness of the deduction for computational efficiency. Some open problems are mentioned.