Rapid prototyping and user-centered design of interactive display-based systems

Much work on display-based ubicomp systems (and rapid prototyping in general) focus on producing proof-of-concept demonstrators, usually to gauge technical feasibility and collect initial user feedback. In our work, we've found that it's often equally important to investigate factors such as use and appropriation and that in some cases, without user studies, technical feasibility can be meaningless. We used rapid prototyping combined with a phased, iterative, and user-centered design approach to develop five display-based ubicomp systems for real-world use over time. In this article, we discuss our aims, approach, and lessons learned. The ubicomp systems that we developed and deployed use rapid prototyping techniques and a user-centered design approach.     

Preference-oriented mining techniques for location-based store search

With the development of wireless telecommunication technologies, a number of studies have been done on the issues of location-based services due to wide applications. Among them, one of the active topics is the location-based search. Most of previous studies focused on the search of nearby stores, such as restaurants, hotels, or shopping malls, based on the user’s location. However, such search results may not satisfy the users well for their preferences. In this paper, we propose a novel data mining-based approach, named preference-oriented location-based search (POLS), to efficiently search for k nearby stores that are most preferred by the user based on the user’s location, preference, and query time. In POLS, we propose two preference learning algorithms to automatically learn user’s preference. In addition, we propose a ranking algorithm to rank the nearby stores based on user’s location, preference, and query time. To the best of our knowledge, this is the first work on taking temporal location-based search with automatic user preference learning into account simultaneously. Through experimental evaluations on the real dataset, the proposed approach is shown to deliver excellent performance.     

Trip planning queries with location privacy in spatial databases

Privacy has become a major concern for the users of location-based services (LBSs) and researchers have focused on protecting user privacy for different location-based queries. In this paper, we propose techniques to protect location privacy of users for trip planning (TP) queries, a novel type of query in spatial databases. A TP query enables a user to plan a trip with the minimum travel distance, where the trip starts from a source location, goes through a sequence of points of interest (POIs) (e.g., restaurant, shopping center), and ends at a destination location. Due to privacy concerns, users may not wish to disclose their exact locations to the location-based service provider (LSP). In this paper, we present the first comprehensive solution for processing TP queries without disclosing a user’s actual source and destination locations to the LSP. Our system protects the user’s privacy by sending either a false location or a cloaked location of the user to the LSP but provides exact results of the TP queries. We develop a novel technique to refine the search space as an elliptical region using geometric properties, which is the key idea behind the efficiency of our algorithms. To further reduce the processing overhead while computing a trip from a large POI database, we present an approximation algorithm for privacy preserving TP queries. Extensive experiments show that the proposed algorithms evaluate TP queries in real time with the desired level of location privacy.     

Using Personal Traces in Context Space: Towards Context Trace Technology

Wearables are often described with a focus on providing the user with wearable information access and communication means. The contextual information retrieval aspect is, however, an essential feature of such systems, as in, for example, the Remembrance Agent [1] where manually entered search-terms are used for presenting relevant situational information, or as in different location-based systems [2]. In this position paper we outline a general framework of contextually aware wearable systems, and suggest how such mechanisms, collecting massive traces of the user context, may lead to several other interesting uses in what we will call context trace technology.     

Modeling by Drawing with Shadow Guidance

Modeling 3D objects is difficult, especially for the user who lacks the knowledge on 3D geometry or even on 2D sketching. In this paper, we present a novel sketch‐based modeling system which allows novice users to create 3D custom models by assembling parts based on a database of pre‐segmented 3D models. Different from previous systems, our system supports the user with visualized and meaningful shadow guidance under his strokes dynamically to guide the user to convey his design concept easily and quickly. Our system interprets the user's strokes as similarity queries into database to generate the shadow image for guiding the user's further drawing and returns the 3D candidate parts for modeling simultaneously. Moreover, our system preserves the high‐level structure in generated models based on prior knowledge pre‐analyzed from the database, and allows the user to create custom parts with geometric variations. We demonstrate the applicability and effectiveness of our modeling system with human subjects and present various models designed using our system.     

Information retrieval and hypertext: competing technologies or complementary access methods

Abstract. Information retrieval typically involves accessing textual information from a database in response to a user's vague information need. Hypertext or hypermedia, on the other hand, involves a user browsing through a database of textual or multimedia information in response to a variety of types of information need. Thus information retrieval can be said to have a searching metaphor while hypertext has a browsing analogy. Initially, these two technologies for information access appear to be very different, almost competitive in nature. In this paper information retrieval systems are briefly reviewed and hypertext systems are also examined. These two techniques for accessing information have been integrated into a prototype system which is described. The system dynamically generates guided tours in response to a user's query and the tour guides the user through the hypertext. Some experiments reporting on the effectiveness of this as an information access strategy are given.     

Using check-in features to partition locations for individual users in location based social network

With location-based social network (LBSN) flourishing, location check-in records offer us sufficient information resource to do relative mining. Among locations visited by a user, those attracting relatively more visits from that user can serve as a support for further mining and improvement for location-based services. Therefore, great significance lies in the partition for visited locations based on a user’s visiting frequency. The aim of our paper is to partition locations for individual users by utilizing classification in machine learning, categorizing the location for a user once he or she makes initial check-in there. After feature extraction for each initial check-in record, we evaluate the contribution of three feature categories. The results show the contribution of different feature categories varies in classification, where social features appear to offer the least contribution. At last, we do a final test on the whole sample, comparing the results with two baselines based on majority voting respectively. The results largely outperform the baselines in general, demonstrating the effectiveness of classification.     

Creating a model of the dynamics of socio-technical groups

Individuals participating in technologically mediated forms of organization often have difficulty recognizing when groups emerge, and how the groups they take part in evolve. This paper contributes an analytical framework that improves awareness of these virtual group dynamics through analysis of electronic trace data from tasks and interactions carried out by individuals in systems not explicitly designed for context adaptivity, user modeling or user personalization. We discuss two distinct cases to which we have applied our analytical framework. These two cases provide a useful contrast of two prevalent ways for analyzing social relations starting from electronic trace data: either artifact-mediated or direct person-to-person interactions. Our case study integrates electronic trace data analysis with analysis of other, triangulating data specific to each application. We show how our techniques fit in a general model of group informatics, which can serve to construct group context, and be leveraged by future tool development aimed at augmenting context adaptivity with group context and a social dimension. We describe our methods, data management strategies and technical architecture to support the analysis of individual user task context, increased awareness of group membership, and an integrated view of social, information and coordination contexts.     

Taxonomy for visualizing location-based information

Location-based data is digital information that has a real-world location. Location-based data can be used for many purposes, such as providing additional information on real-world objects or helping a user in a specific task. Access to such data can be provided in many ways, for example, with augmented reality (AR) systems. AR techniques can help its user in various tasks and the AR data can be presented to the user in various ways, depending on the task at hand. The different visualizations that can be used are heavily dependent on the hardware platform and, thus, all technologies are not suitable for every situation. This paper studies two factors that affect the visualization of location-based data. The two factors are the environment model they use, ranging from three dimensions (3D) to no dimensions (0D) at all; and the viewpoint, whether it is a first-person or a third-person view. As a result, we define a taxonomy for visualizing location-based data, where each model–view (MV) combination is referred to using its MV number. We also present numerous case studies with different MV values.     

带有空间特性角色约束

空间数据库系统和基于移动用户位置的信息服务系统对访问控制模型具有特殊要求--用户地理位置的变化通常会引起用户权限的动态变化.提出一个支持空间特性的角色访问控制模型Spatial-RBAC,详细讨论了在空间环境下的空间区域约束、空间职责分离约束和空间角色激活基数约束.这些约束分别用来控制角色分配、角色状态改变、角色权限分配和角色激活等操作,给传统的基于角色的访问控制模型增加了空间安全描述能力.在安全空间数据库应用中,为了有效地标识用户地理位置的变化,避免不必要的计算,还给出了判断用户当前扮演的角色集的有效作用域的算法,提高了Spatial-RBAC模型的实用性.     

WSN中基于UWB和移动信标点的安全定位方法

随着无线传感器网络(WSN)理论和技术的发展,基于位置的应用(如基于位置的存取控制)已成为一种新的需求.然而已有的定位系统没有考虑到特定环境下攻击者利用放大器、定向天线或者通过被俘获节点进行攻击的情形.本文利用超宽带技术(UWB)的优点,提出一种基于UWB和移动信标点的安全定位方法,更适合WSN中基于位置估计的应用需求.该方法首先定位出网络中用户节点的位置,然后进行位置验证,去除恶意信标点,最终实现准确定位.通过实验表明了该方法的有效性.     

Preventing Location-Based Identity Inference in Anonymous Spatial Queries

The increasing trend of embedding positioning capabilities (for example, GPS) in mobile devices facilitates the widespread use of location-based services. For such applications to succeed, privacy and confidentiality are essential. Existing privacy-enhancing techniques rely on encryption to safeguard communication channels, and on pseudonyms to protect user identities. Nevertheless, the query contents may disclose the physical location of the user. In this paper, we present a framework for preventing location-based identity inference of users who issue spatial queries to location-based services. We propose transformations based on the well-established K-anonymity concept to compute exact answers for range and nearest neighbor search, without revealing the query source. Our methods optimize the entire process of anonymizing the requests and processing the transformed spatial queries. Extensive experimental studies suggest that the proposed techniques are applicable to real-life scenarios with numerous mobile users.     

Video stereolization: combining motion analysis with user interaction

We present a semiautomatic system that converts conventional videos into stereoscopic videos by combining motion analysis with user interaction, aiming to transfer as much as possible labeling work from the user to the computer. In addition to the widely used structure from motion (SFM) techniques, we develop two new methods that analyze the optical flow to provide additional qualitative depth constraints. They remove the camera movement restriction imposed by SFM so that general motions can be used in scene depth estimation-the central problem in mono-to-stereo conversion. With these algorithms, the user's labeling task is significantly simplified. We further developed a quadratic programming approach to incorporate both quantitative depth and qualitative depth (such as these from user scribbling) to recover dense depth maps for all frames, from which stereoscopic view can be synthesized. In addition to visual results, we present user study results showing that our approach is more intuitive and less labor intensive, while producing 3D effect comparable to that from current state-of-the-art interactive algorithms.     

Evaluating the benefits of multimodal interface design for CoMPASS—a mobile GIS

The context of mobility raises many issues for geospatial applications providing location-based services. Mobile device limitations, such as small user interface footprint and pen input whilst in motion, result in information overload on such devices and interfaces which are difficult to navigate and interact with. This has become a major issue as mobile GIS applications are now being used by a wide group of users, including novice users such as tourists, for whom it is essential to provide easy-to-use applications. Despite this, comparatively little research has been conducted to address the mobility problem. We are particularly concerned with the limited interaction techniques available to users of mobile GIS which play a primary role in contributing to the complexity of using such an application whilst mobile. As such, our research focuses on multimodal interfaces as a means to present users with a wider choice of modalities for interacting with mobile GIS applications. Multimodal interaction is particularly advantageous in a mobile context, enabling users of location-based applications to choose the mode of input that best suits their current task and location. The focus of this article concerns a comprehensive user study which demonstrates the benefits of multimodal interfaces for mobile geospatial applications.     

SKIF-P: a point-based indexing and ranking of web documents for spatial-keyword search

There is a significant commercial and research interest in location-based web search engines. Given a number of search keywords and one or more locations (geographical points) that a user is interested in, a location-based web search retrieves and ranks the most textually and spatially relevant web pages. In this type of search, both the spatial and textual information should be indexed. Currently, no efficient index structure exists that can handle both the spatial and textual aspects of data simultaneously and accurately. Existing approaches either index space and text separately or use inefficient hybrid index structures with poor performance and inaccurate results. Moreover, most of these approaches cannot accurately rank web-pages based on a combination of space and text and are not easy to integrate into existing search engines. In this paper, we propose a new index structure called Spatial-Keyword Inverted File for Points to handle point-based indexing of web documents in an integrated/efficient manner. To seamlessly find and rank relevant documents, we develop a new distance measure called spatial tf-idf. We propose four variants of spatial-keyword relevance scores and two algorithms to perform top-k searches. As verified by experiments, our proposed techniques outperform existing index structures in terms of search performance and accuracy.     

The location-based paradigm for replication: Achieving efficiencyand availability in distributed systems

Replication techniques for transaction-based distributed systems generally achieve increased availability but with a significant performance penalty. We present a new replication paradigm, the location-based paradigm, which addresses availability and other performance issues. It provides availability similar to quorum-based replication protocols but with transaction-execution delays similar to one-copy systems. The paradigm further exploits replication to improve performance in two instances. First, it takes advantage of local or nearby replicas to further improve the response time of transactions, achieving smaller execution delays than one-copy systems. Second, it takes advantage of replication to facilitate the independent crash recovery of replica sites-a goal which is unattainable in one-copy systems. In addition to the above the location-based paradigm avoids bottlenecks, facilitates load balancing, and minimizes the disruption of service when failures and recoveries occur. In this paper we present the paradigm, a formal proof of correctness, and a detailed simulation study comparing our paradigm to one-copy systems and to other approaches to replication control     

A content search system considering the activity and context of a mobile user

People routinely carry mobile devices in their daily lives and obtain a variety of information from the Internet in many different situations. In searching for information (content) with a mobile device, a user’s activity (e.g., moving or stationary) and context (e.g., commuting in the morning or going downtown in the evening) often change, and such changes can affect the user’s degree of concentration on his or her mobile device’s display and information needs. Therefore, a search system should provide the user with an amount of information suitable for the current activity and a type of information suitable for the current context. In this study, we present the design and implementation of a content search system that considers a mobile user’s activity and context, with the goal of reducing the user’s operation load for content search. The proposed system switches between two kinds of content search systems according to the user’s activity: the location-based content search system is activated when the user is stationary (e.g., standing and sitting), while a menu-based content search system is activated when the user is moving (e.g., walking). Both systems present information according to user context. The location-based system presents detailed information via menus and a map according to location-based categories. The menu-based system presents only a few options to enable users to get content easily. Through user experiments, we confirmed that participants could get desired information more easily with this system than with a commercial search system.     

Anonymous Query Processing in Road Networks

The increasing availability of location-aware mobile devices has given rise to a flurry of location-based services (LBSs). Due to the nature of spatial queries, an LBS needs the user position in order to process her requests. On the other hand, revealing exact user locations to a (potentially untrusted) LBS may pinpoint their identities and breach their privacy. To address this issue, spatial anonymity techniques obfuscate user locations, forwarding to the LBS a sufficiently large region instead. Existing methods explicitly target processing in the euclidean space and do not apply when proximity to the users is defined according to network distance (e.g., driving time through the roads of a city). In this paper, we propose a framework for anonymous query processing in road networks. We design location obfuscation techniques that: 1) provide anonymous LBS access to the users and 2) allow efficient query processing at the LBS side. Our techniques exploit existing network database infrastructure, requiring no specialized storage schemes or functionalities. We experimentally compare alternative designs in real road networks and demonstrate the effectiveness of our techniques.     

The Well Mannered Wearable Computer

In this paper we describe continuing work being carried out as part of the Bristol Wearable Computing Initiative. We are interested in the use of context sensors to improve the usefulness of wearable computers. A CyberJacket incorporating a Tourist Guide application has been built, and we have experimented with location and movement sensing devices to improve its performance. In particular, we have researched processing techniques for data from accelerometers which enable the wearable computer to determine the user’s activity. We have experimented with, and review, techniques already employed by others; and then propose new methods for analysing the data delivered by these devices. We try to minimise the number of devices needed, and use a single X-Y accelerometer device. Using our techniques we have adapted our CyberJacket and Tourist Guide to include a multimedia presentation which gives the user information using different media depending on the user’s activity as well as location.