Dynamic topological predicates and notifications in moving objects databases

This work addresses the problem of efficient reactive management of topological predicates in MOD (Moving Objects Databases) settings. Detecting the satisfiability of such predicates in mobile and dynamic environments requires management of continuous and persistent conditions. We introduce two dynamical topological predicates: moving-along and moving-towards and we present efficient algorithmic solutions for their processing. Based on this, we subsequently take a deeper insight in the behavioral aspects of a MOD which manages them and we argue that the traditional ECA (Event Condition Action) paradigm, while it may ensure correct behavior, is not well-suited for enabling the users to declaratively specify some of the parameters that may affect the efficiency aspect of the reactive behavior. Towards this end, we introduce the (ECA)2 (Evolving and Context-Aware Event-Condition-Action) paradigm as a tool for specification of the triggers used by a MOD that handles requests which span over a time-interval in dynamic environments.