Spatial Data Warehouse Modelling

is concerned with multidimensional data models for spatial data warehouses. It first draws a picture of the research area, and then introduces a novel spatial multidimensional data model for spatial objects with geometry: the Multigranular Spatial Data warehouse (MuSD). The main novelty of the model is the representation of spatial measures at multiple levels of geometric granularit

Semantic Integration in MADS Conceptual Model

Our vision of a viable way for transparent and meaningful processing of heterogeneous spatio-temporal data is to put data semantics in the foundation of an integration process. We present and correlate means of integration as components of the mediation level of an interoperable system. For our domain of interest we present MADS domain ontologies and MADS conceptual data model dedicated to modeling of spatio-temporal data. Using as example two MADSschemas we outline an integration methodology based on semantic interschema correspondence assertions and integration goals

Predicting Transportation Modes of GPS Trajectories using Feature Engineering and Noise Removal

Understanding transportation mode from GPS (Global Positioning System) traces is an essential topic in the data mobility domain. In this paper, a framework is proposed to predict transportation modes. This framework follows a sequence of five steps: (i) data preparation, where GPS points are grouped in trajectory samples; (ii) point features generation; (iii) trajectory features extraction; (iv) noise removal; (v) normalization. We show that the extraction of the new point features: bearing rate, the rate of rate of change of the bearing rate and the global and local trajectory features, like medians and percentiles enables many classifiers to achieve high accuracy (96.5%) and f1 (96.3%) scores. We also show that the noise removal task affects the performance of all the models tested. Finally, the empirical tests where we compare this work against state-of-art transportation mode prediction strategies show that our framework is competitive and outperforms most of them.Comment: 6 page

Conflict in pedestrian networks

Encouraging pedestrian activity is increasingly recognised as beneficial for public health, the environment and the economy. As our cities become more crowded, there is a need for urban planners to take into account more explicitly pedestrian needs. The term that is now in use is that a city should be ‘walkable’. For route planning, whereas much attention has been given to shortest path, in distance or time, much less attention has been paid to flow levels and the difficulties they pose on the route. This paper considers problems posed by conflicting paths, for example cross-traffic. We use network centrality measures to make a first estimate of differing levels of conflict posed at the network nodes. We take special note of the role of collective motion in determining network usage. A small case study illustrates the method

Evolving Objects in Temporal Information Systems

This paper presents a semantic foundation of temporal conceptual models used to design temporal information systems. We consider a modelling language able to express both timestamping and evolution constraints. We conduct a deeper investigation of evolution constraints, eventually devising a model-theoretic semantics for a full-fledged model with both timestamping and evolution constraints. The proposed formalization is meant both to clarify the meaning of the various temporal constructors that appeared in the literature and to give a rigorous definition, in the context of temporal information systems, to notions like satisfiability, subsumption and logical implication. Furthermore, we show how to express temporal constraints using a subset of first-order temporal logic, i.e. DLRUS, the description logic DLR extended with the temporal operators Since and Until. We show how DLRUS is able to capture the various modelling constraints in a succinct way and to perform automated reasoning on temporal conceptual models

Semantics of Database Transformations

Database transformations arise in many different settings including database integration, evolution of database systems, and implementing user views and data entry tools. This paper surveys approaches that have been taken to problems in these settings, assesses their strengths and weaknesses, and develops require ments on a formal model for specifying and implementing database transformations. We also consider the problem of insuring the correctness of database transformations. In particular, we demonstrate that the usefulness of correctness conditions such as information preservation is hindered by the interactions of transformations and database constraints, and the limited expressive power of established database constraint languages. We conclude that more general notions of correctness are required, and that there is a need for a uniform formalism for expressing both database transformations and constraints, and reasoning about their interactions, Finally we introduce WOL, a declarative language for specifying and implementing database transformations and constraints. We briefly describe the WOL language and its semantics, and argue that it addresses many of the requirements on a formalism for dealing with general database transformations