On the Expressiveness of Query

We explore the expressive power of the query language of rst order logic with linear constraints. Natural queries are shown to be expressible in this language in a non-trivial fashion. We further investigate the ability of the language to capture certain properties that seem desirable in spatial databases. We show that, although these properties are captured in a certain extent, there are still cases where the language has counter-intuitive behavior. In this context, we show that FO+linear cannot distinguish between databases that carry similar spatial characteristics , e.g., two diierent ellipses.