This paper introduces the problem of modeling urban transportation systems in a database where certain aspects of the data are probabilistic in nature. The transportation network is composed of multiple modes (e.g., automobile, bus, train, pedestrian) that the user can alternate between. A tripa path between an origin and destination subject to some constraints -is the central concept. How these trips and the network can be represented as both a graph and relational model, as well as the requirements for querying are the main contributions of this paper. A set of operators are defined to work over these transportation concepts and they are integrated within a SQL-like syntax to express queries over the uncertain transportation network. Additionally, the paper shows how this model can be integrated within other moving objects and spatio-temporal data models, and how these graph-based queries can be processed.

Navigating large, urban transportation networks is a complicated task. A user needs to negotiate the available modes of transportation, their schedules, and how they are interconnected. In this paper we present a Natural Language interface for trip planning in complex multimodal urban transportation networks. Our objective is to provide robust understanding of complex requests while giving the user flexibility in their language.We designed TRANQUYL, a Transportation Query Language for trip planning; we developed a usercentric ontology, that defines the concepts covered by the interface and allows for a broad vocabulary. NL2TRANQUYL, the software system built on these foundations, translates English requests into formal TRANQUYL queries. Through a detailed intrinsic evaluation, we show that NL2TRANQUYL is highly accurate and robust with respect to paraphrasing of requests as well as handling fragmented or telegraphic requests.

Abstract