Catálogo de publicaciones - libros

Recently, with the development of wireless communications and mobile computing, interest in mobile computing is rising. Mobile computing can be regarded as an environment where a user carries mobile devices and shares resources with a server via wireless communications. A mobile database, which can be used in the various fields, refers to a database used in these mobile devices. Especially, LBS which utilizes location information of users becomes an essential field of mobile computing. In order to support LBS in the mobile environment, there must be an Embedded Spatial MMDBMS that can efficiently manage large spatial data in spatial mobile devices. Therefore, in this paper, we developed an Embedded Spatial MMDBMS, extended from the HSQLDB which is an existing MMDBMS for PC, to manage spatial data efficiently in spatial mobile devices. The Embedded Spatial MMDBMS adopted the spatial data model proposed by ISO, provided the arithmetic coding method suitable for spatial data, and supported the efficient spatial index suitable for spatial mobile devices. In addition, the system offered the spatial data display capability and supported the data caching and synchronization capability between the Embedded Spatial MMDBMS and the GIS server.

Recently, the need for LBS (Location Based Services) is increasing due to the widespread of mobile computing devices and positioning technologies. In LBS, there are many applications that need to manage moving objects (e.g. taxies, persons). The trajectories or the positions of moving objects are displayed on the map by using GIS. However, it is hard to use GIS or traditional relational database systems to manage moving objects. Modeling consistent information about the location of continuously moving objects and processing motion-specific queries is challenging problem. The previous studies suggested several query languages to retrieve moving objects. However, they do not propose DDL (Data Definition Language) and do not support full functions that are necessary. In this paper, we formally define a data model and data type for moving objects and propose MOQL (Moving Objects Query Language) which is a convenient interface and tool for developers. MOQL has the following features. First, it supports DDL to insert/delete/update the positions of moving objects. Second, it can be used to retrieve the trajectories of moving objects. Third, it defines several functions to manage spatial or temporal properties of moving objects.

Location-based services (LBS) constitute an emerging application domain involving spatio-temporal databases. In this paper, i) we propose a classification of LBS, depending on whether the user (query object) and the data objects are moving or not and ii) we provide algorithms for the efficient support of real applications, for every class. We also survey recent work in query processing for the proposed LBS algorithms and sketch open issues for future research.

In pedestrian navigation, navigators are free to choose any passable way. Because of this characteristic, accurate route instructions are important when navigating from waypoint to waypoint. In this paper, a theoretical framework is described for dealing with position uncertainty in pedestrian guiding systems. Stages of closeness are defined based on the topological relation between the navigator and a waypoint. These stages of closeness allow for refining route instructions and, therefore, leading to more accurate navigation and increased efficiency of the system.

We propose a model for management of vector multiresolution geodata in a client-server framework which takes into account constraints related to mobile context (limitations of storage and transfer rate). The amount of data exchanged between client and server can be minimized by reusing data already available on the client side with the concept of “increment”. An increment corresponds to a sequence of operations allowing the reconstruction of an object in one resolution from the same object in another resolution available in the client’s cache.

Line simplification is the most commonly used operation in map generalisation. In many commercial Geographic Information Systems (GIS), line simplification is performed by applying the classical Ramer-Douglas-Peucker (RDP) algorithm. However, such an algorithm has the drawback of not guaranteeing the preservation of topological consistency. This requires a posteriori checks to ensure that unwanted intersections introduced by the application of the algorithm get rectified. To overcome this problem, Saalfeld proposed a modification of the classical RDP algorithm based on the fact that, while generalising a polyline, conflicts can only occur with vertices of other polylines that lie within its convex hull. In this paper we propose an improvement to Saalfeld’s algorithm to detect possible self-intersections of a simplified polyline more efficiently. This improves the performance especially when generalising very large datasets. Nevertheless, the processing time is still not acceptable for real-time web mapping. Therefore, we have integrated our algorithm into a web mapping system that pre-computes a sequence of topologically consistent map representations, stores them on the server, and transmits them progressively upon request. We present experimental results of the performance of the algorithm as well as results of the transmission system.

Stored map services in mobile devices are being commercialized for mobile and wireless environment such as cellular phones. In order to ensure the quality and accuracy of map, the update on the source map must be reflected automatically to mobile devices. Due to the expensive communication cost and lack of hardware capacity of mobile devices, we should find a compromising solution between the transmission of an entire map and the transmission of only update logs to mobile devices. The transmission of the completely processed whole map results in an expensive communication cost, while simple transfer of update logs requires a large amount of processing to maintain geometric and topological consistency between multiple LODs(Level of Details). In this paper, we first propose a framework of update mechanism in mobile environments where the map data is stored on each mobile device. This framework provides an efficient strategy for processing an update and its propagation to multiple LODs without an expensive cost of communication and large amount of processing at mobile devices. Secondly, several methods are introduced to maintain topological consistency between LODs depending on the type of generalization operators. Finally, we propose an extended SVG(Simple Vector Graphics) to be used as a transfer format of update message to mobile devices.

This paper addresses the methodological issues of developing and visualising added value geo-enabled content for mobile information systems. The research was carried out under the framework of WebPark, an EC-IST R&D project that developed a location aware application for nature/protected areas. The evaluation of existing information sources – tourism information, research data, and multimedia content – revealed that the tourism information and multimedia content analysed did not have an active geographic component and the geographic research data (e.g. animal counts/observations) had a clear mismatch as regards the visitors’ information needs. Therefore, different types of data processing were developed and performed in order to render existing information sources useful for location-based services. Data preparation also included building hierarchical data structures (quadtrees and hierarchical stream ordering). The paper shows how these data structures are exploited to facilitate real-time generalisation in order to efficiently present thematic point data on portable devices. Finally, three key lessons for geo-enabling location-based services are presented.

The history management of vehicles is important in telematics applications. To process queries for history data, trajectories, we generally use trajectory-preserving index schemes based on the trajectory preservation property. This property means that a leaf node only contains segments belonging to a particular trajectory, regardless of the spatiotemporal locality of segments. The sacrifice of spatiotemporal locality, however, causes the index to increase the dead space of MBBs of non-leaf nodes and the overlap between the MBBs of nodes. Therefore, an index scheme for trajectories shows good performance with trajectory-based queries, but not with coordinate-based queries, such as range queries. We propose a new index scheme that improves the performance of range queries without reducing performance with trajectory-based queries. In the new index scheme using the , two entries in different nodes are exchanged to minimize the dead spaces of the MBBs of the corresponding nodes.

Location Alerting Service is a push service that informs users whether predefined conditions be satisfied based on periodic acquisitions of location data from mobile terminals for several purposes such as safety. Polling the location of terminal is one of the basic functional requirements of this service. In this paper, an analysis of the location polling technique will be given, we will propose an efficient location polling algorithm and present the results of experiments with this algorithm.