Adding a Path Connectedness Operator to FO + polyChris
نویسندگان
چکیده
The languages FO +poly and FO +linear have been proposed as a foundation for spatial database query languages. We extend both languages with a parameterised path-connectivity predicate, Pconn, to study spatial queries involving connectivity. We show that: FO +linear +Pconn; FO +poly +Pconn?2D, are closed and have NC data complexity, and FO + poly + Pconn ?3D is closed and has PTIME data complexity. We also examine the expressiveness of FO + poly + Pconn and give some queries for which Pconn is essential.
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تاریخ انتشار 1999