The advances in positioning and communication technologies make it possible to collect and transfer trajectories of moving vehicles. In addition to some basic applications such as navigation

traffic data can be extracted from vehicle trajectories

such as average moving velocity and travel time on a road segment in a given time period. The network and spatio-temporal characteristics of trajectories

however

make it difficult to evaluate queries applied to them. As a result

many studies have focused on developing index structures and methods for trajectory data. However

few of them have presented the corresponding data query language. In this paper

we discussed some issues related to trajectory data query language

including the definition of the connectivity-oriented data query language (CQL)

the classification of CQL

and its implementation based on an index structure proposed by previous study. We further discussed a prototype for vehicle trajectory data query based on CQL in terms of its structure and implementation.