Query autocompletion is an important and practical technique when users want to search for desirable information. As mobile devices become more and more popular, one of the main applications is location-aware service, such as Web mapping. In this paper, we propose a new solution to location-aware query autocompletion. We devise a trie-based index structure and integrate spatial information into trie nodes. Our method is able to answer both range and top-k queries. In addition, we discuss the extension of our method to support the error tolerant feature in case user's queries contain typographical errors. Experiments on real datasets show that the proposed method outperforms existing methods in terms of query processing performance.

The development of smart devices has led to the growth of Location-Based Social Networking Services (LBSNSs). In this paper, we introduce an l-Close Range Friends query that finds all l-hop friends of a user within a specified range. We also propose a query processing method on Social Grid Index (SGI). Using real datasets, the performance of our method is evaluated.

Given a set of positive-weighted points and a query rectangle r (specified by a client) of given extents, the goal of a maximizing range sum (MaxRS) query is to find the optimal location of r such that the total weights of all points covered by r is maximized. In this paper, we address the problem of processing MaxRS queries over road network databases and propose two new external memory methods. Through a set of simulations, we evaluate the performance of the proposed methods.

Context awareness is one of the ultimate goals of ubiquitous computing, and spatial information plays an important role in building context awareness. In this paper, we propose a new interoperable spatial information model, which is based on ucode relation (ucR) and Place Identifier (PI), for realizing ubiquitous spatial infrastructure. In addition, we propose a design environment for spatial information database using our model. Our model is based on ucode and its relation. ucode is 128 bits number and the number itself has no meaning. Hence, it is difficult to manage the relation between ucodes without using a tool. Our design environment provides to describe connection between each ucode visually and is able to manipulate data using the target space map interactively. To evaluate the proposed model and environment, we designed three spaces using our tool. In addition, we developed a web application using our spatial model. From evaluation, we have been showed that our model is effective and our design environment is useful to develop our spatial information model.

A range top-k query returns the topmost k records in the order set by a measure attribute within a specified region of multi-dimensional data. The range top-k query is a powerful tool for analysis in spatial databases and data warehouse environments. In this paper, we propose an algorithm to answer the query by selectively traversing an aggregate R-tree having MAX as the aggregate values. The algorithm can execute the query by accessing only a small part of the leaf nodes within a query region. Therefore, it shows good query performance regardless of the size of the query region. We suggest an efficient pruning technique for the priority queue, which reduces the cost of handling the priority queue, and also propose an efficient technique for leaf node organization to reduce the number of node accesses to execute the range top-k queries.

This paper proposes a new framework of managing virtual spaces based on spatial databases as an extension of VRML-based systems. The framework is suitable for treating continuous virtual spaces and for managing the quality of service (QoS) of the virtual spaces depending on user's operations and situations of computer resources. Levels of detail (LoD) of 3D objects is the most important rule for rendering scenes dynamically while managing the QoS. This paper describes a method of managing the QoS depending on the LoD in the form of spatial queries. An advantage of the framework is that spatial databases can incrementally construct virtual spaces in clients using differential descriptions based on VRML, that is, DVRML, proposed in this paper. Dynamic spatial data such as avatar's movement and real-time multimedia data such as videos should be shared by all participants in a virtual space in real time. Our framework can also handle dynamic spatial data by means of real-time updating of some spatial objects in spatial databases as well as static spatial data. We developed some experimental applications based on the framework in order to prove that it is feasible for networked virtual spaces with video components.