Landslides constitute one of the most important natural hazards in many countries all over the world. Due to such fatalities, a lot of attention is dedicated to the safety assessment and monitoring of assets of public relevance for either local or state administrations. Railway stations and lines represent a relevant category of elements because of their intrinsic economic value and because their damage may cause human casualties as well. However, if attempts to assess the safety of assets consider large geographic areas, the number of assets potentially exposed at risk would be very high. So, the opportunities to exploit real-time monitoring technologies, e.g. Wireless Sensor Networks (WSN), would be too much costly. To mitigate such issues, this paper presents an innovative framework for a cost-effective monitoring of landslides applied to railway stations and lines that combines the use of WSN technologies with an existing Geographical Information Service (GIS) based ranking method. A case study focused on the Abruzzo Region of Italy shows the potential benefits of such an integrated approach.

The ability to run spatial queries is extremely useful for wireless sensor networks. Spatial query execution has been extensively studied in the context of centralized spatial databases; however because of the energy and bandwidth limitation of sensor nodes these solutions are critical to wireless sensor networks. In this paper, we propose an extension of TinyDB suitable to manage the location of sensor nodes and, hence, able to process besides standard queries, spatial queries as well. The proposal has been implemented and validated.

A set of topological invariants for relations between lines embedded in the 2-dimensional Euclidean space is given. The set of invariants is proven to be necessary and sufficient to characterize topological equivalence classes of binary relations between simple lines. The topology of arbitrarily complex geometric scenes is described with a variation of the same set of invariants. Polynomial time algorithms are given to assess topological equivalence of two scenes. Invariants and efficient algorithms is due to application areas of spatial database systems where a model for describing topological relations between planar features is sought.

The amount of memory required by perfect hash functions at retrieval time is one of the primary issues to be taken into account when looking for such functions. This paper gives empirical evidence about the effectiveness of a strategy that is suitable for significantly reducing the memory requirements of the order-preserving minimal perfect hash function proposed by Z.J. Czech et al. (Inf. Proc. Lett., vol. 43, pp. 257-64, Oct. 1992).

The 4-intersection, a model for the representation of topological relations between two-dimensional objects with connected boundaries and connected interiors, is extended to cover topological relations between two-dimensional objects with arbitrary holes, called regions with holes. Each region with holes is represented by its generalized region—the union of the object and its holes—and the closure of each hole. The topological relation between two regions with holes, A and B, is described by the set of all individual topological relations between (1) A's generalized region and B's generalized region, (2) A's generalized region and each of B's holes, (3) B's generalized region with each of A's holes, and (4) each of A's holes with each of B's holes. As a side product, the same formalism applies to the description of topological relations between 1-spheres. An algorithm is developed that minimizes the number of individual topological relations necessary to describe a configuration completely. This model of representing complex topological relations is suitable for a multi-level treatment of topological relations, at the least detailed level of which the relation between the generalized regions prevails. It is shown how this model applies to the assessment of consistency in multiple representations when, at a coarser level of less detail, regions are generalized by dropping holes.

Two levels of data abstraction, namely conceptual and logical, are essential in the process of designing an object-oriented geographic database. The aim of the present article is to establish a consistent framework for this bilevel design. At the conceptual level, we develop an object-oriented model useful for organizing the designer's knowledge about a geographic application in terms of the basic concepts of the object-oriented paradigm. Both conceptual abstraction primitives (namely, classification, generalization, and aggregation) and a spatial abstraction primitive (namely, location) are discussed. The dynamic part of the model is due to the methods associated with objects. At the logical level, we propose an object-oriented structure of classes and instances, which is uniform with the conceptual model and, therefore, facilitates the conceptual logical mapping. On the whole, the model-based approach adopted in this article offers object orientation, conceptual abstraction, and system extendibility. © 1994 John Wiley & Sons, Inc.

Mathematical software is devoted to solving problems involving matrix computation and manipulation. The main problem limiting the reusability of existing mathematical software is that programs are often not initially designed for being reused. Therefore, it is hard to find programs that can be easily reused. A programming methodology useful for designing and implementing reusable code is presented. A portion of code designed and implemented for being reused is called a unit. The units are self-contained software components featuring a high degree of information hiding. This way of organizing software facilitates the reuse process and improves the understandability of units. To speed up the implementation process, a system supporting the reusability of units from an existing software library is particularly useful. The functionality of the EasyCard system, which creates, maintains, and queries a catalog of units is discussed.>

In geographic maps, objects are represented in a context extremely rich of relationships among them, either one-to-one or many-to-many. Unfortunately, all these relationships can not be directly represented in the database scheme. Nevertheless, it should be possible to show them to the user during the interaction. To manage this problem, the authors refer to a two-level database architecture with an object-oriented data model at the bottom level (the logic level), and an interaction model at the top level. The spatial data model given is an essential part of the interaction model. The spatial data model is a conceptual tool that enhances the object-oriented model with spatial relationships between objects. The basic objectives of the spatial data model are outlined: to point out the relationships among objects to be shown in the views, to define data structures suitable for navigating among database objects, and to provide a simple and powerful calculus for posing spatial queries against the database.>

A new dynamic approach to the problem of determining the correct interpretation of a logically independent query to a relational database is described. The proposed disambiguating process is based on a simple user-system dialogue that consists in a sequence of decisions about the relevance (or not) of an attribute with respect to the user interpretation