Formalization of network-constrained moving object queries with application to benchmarking

In this paper, we first categorize the various types of Network-constrained moving object queries. We then propose benchmarks that can be used to compare the performance of systems and indexing schemes that are proposed for handling these types of queries. Network-constrained moving objects are objects that move in a specific network, such as vehicles that are constrained to move in a road (traffic) network. Our query categories are based on the Network-constrained moving object model presented by [4, 6, 14]. We formally define comprehensive categories of typical queries, based on whether the conditions involve space (point versus region), time (point versus interval), and object id. The categories are based on the various combinations of these features. We describe the types of queries as Relational Calculus expressions, based on the query constraints. We focus on three main constraints: Spatial constraints, Temporal constraints, or/and moving object ID constraints. For each types of query, we identify the types of results, and give examples to clarify the query types. This work can define a benchmark for the performance of different types of systems and indexes that are designed to answer queries on Network-constrained moving objects data. Certain indexes/systems may work well for some query categories but perform poorly for other types of queries.