What we talk about when we talk about context

The emergence of ubiquitous computing as a new design paradigm poses significant challenges for human-computer interaction (HCI) and interaction design. Traditionally, HCI has taken place within a constrained and well-understood domain of experience—single users sitting at desks and interacting with conventionally-designed computers employing screens, keyboards and mice for interaction. New opportunities have engendered considerable interest in context-aware computing—computational systems that can sense and respond to aspects of the settings in which they are used. However, considerable confusion surrounds the notion of context—what it means, what it includes and what role it plays in interactive systems. This paper suggests that the representational stance implied by conventional interpretations of context misinterprets the role of context in everyday human activity, and proposes an alternative model that suggests different directions for design.

Uncertainty handling in rule-based mobile context-aware systems

Uncertainty handling is one of the most important aspects of modelling of context-aware systems. It has direct impact on the adaptability, understood as an ability of the system to adjust to changing environmental conditions or hardware configuration (missing data), changing user habits (ambiguous concepts), or imperfect information (low quality sensors). In mobile context-aware systems, data is most often acquired from device’s hardware sensors (like GPS, accelerometer), virtual sensors (like activity recognition sensor provided by the Google API) or directly from the user. Uncertainty of such data is inevitable, and therefore it is obligatory to provide mechanisms for modelling and processing it. In this paper, we propose three complementary methods for dealing with most common uncertainty types present in mobile context-aware systems. We combine modified certainty factors algebra, probabilistic interpretation of rule-based model, and time-parametrised operators into a comprehensive toolkit for modelling and building robust mobile context-aware systems. Presented approach was implemented and evaluated on the practical use-case.     

DaaS: Cloud-based mobile Web service discovery

The proliferation of smartphones and the recent advancement in ubiquitous wireless access have made mobile Web services more possible than ever before. However, finding relevant Web services that can match requests and fit user context remains a major concern. The challenges facing Web service discovery are further magnified by the stringent constraints of mobile devices and the inherit complexity of wireless heterogeneous networks. Cloud computing, with its flexible design and theoretically unlimited computing resources, is a viable approach to bootstrapping Web service discovery. The cloud can build bridges between mobile devices, as a convenient ubiquitous interface, and a backbone infrastructure with abundant computing resources. This paper introduces “Discovery as a service (Daas)”, a novel cloud-based discovery framework that addresses the core components of mobile Web service discovery. The DaaS framework lays the foundation of efficient mobile Web service discovery that takes into consideration user preferences and context. The experimental validation and performance evaluation demonstrate that DaaS can effectively rank relevant services according to the various user context and preferences, in addition to enhancing the precision of the discovered services. The prototype also shows that Web service clustering for discovery significantly improves the overall response time, while the cloud maintains scalability according to prespecified performance criteria.     

Social functions of location in mobile telephony

Location appears to be one of the most important aspects of context in mobile communication. It is a complex piece of information involving several levels of detail. Location intertwines with other relevant aspects of context: the parties’ present activity, relative time and identities. The analysis of mobile conversations provides insights into the functions of “location” for mobile users. Most mobile calls involve a sequence in which location is reported. Location is made relevant by the parties’ activities. Location telling takes place in five different activity contexts during mobile calls. Location may be an index of interactional availability, a precursor for mutual activity, part of an ongoing activity, or it may bear emergent relevance for the activity or be presented as a social fact. Typically, joint activities make relevant spatio-temporal location such as distance in minutes from the meeting point via the vehicle used. For users, location does not appear to be relevant in purely geographical terms.     

The impact of use context on mobile services acceptance: The case of mobile ticketing

The most important factor in the decision to adopt mobile systems is user perception of their value. However, behavioral theory suggests that context affects user attitude and therefore influences acceptance. We therefore hypothesized that the benefits of mobile systems should be evaluated against users’ contextual needs and that reduced dependence on time and place required providing service at any time and place needed by the user. Mental costs or costs of learning to use the system, however, may not be evaluated in the same way, because system use and learning about it are acts with different contexts. Our findings advance knowledge of IT adoption and suggest that we should start to identify the contexts of both the benefits of use and in learning to use the system.     

An empirical investigation of mobile ticketing service adoption in public transportation

In this paper, we present results from a study of mobile ticketing service adoption in public transportation. The theoretical background of the study is based on technology adoption and trust theories, which are augmented with concepts of mobile use context and mobility. Our empirical findings from analyses of a survey data suggest that compatibility of the mobile ticketing service with consumer behavior is a major determinant of adoption. Mobility and contextual factors, including budget constraints, availability of other alternatives, and time pressure in the service use situation were also found to have a strong effect on the adoption decision. Our findings suggest that contextual and mobile service-specific features are important determinants of mobile service adoption and should thus be integrated into the traditional adoption models.     

Examining proactiveness and choice in a location-aware mobile museum guide

Cultural heritage is an area that has recently drawn research attention, especially for exploring ways to harness novel mobile technologies for supporting visitors. The main benefit of these novel technologies is their ability to provide personalized, context-aware information services to their users. However, the use of context-awareness is connected to a fundamental issue of proactiveness - should the system keep the user in control all the time and only respond to user requests, or should the system take initiative and propose its services when needed? Proactiveness of mobile visitors’ guides brings with it a possibility for better service to the user at the cost of taking control out of the user’s hand. The amount of choice given to visitors is another key issue. With the vast amount of information available for each exhibit, adaptation of the amount of information by limiting the number of content items, could be warranted to filter the information according to the visitors needs. However, it is not clear how reducing choice in terms of the number of content items that are presented to the visitor affects visitor behavior and satisfaction. We examined these issues in a controlled user study conducted with actual museum visitors; comparing usage, behavior patterns, and attitudes of visitors using three versions of a location-aware mobile museum guide.     

Involving users early on in the design process: closing the gap between mobile information services and their users

Designing mobile information services, including mobile Internet services, mobile banking, interactive mobile television, location-based services etc. that capture a mass market has not been easy, and there have been many disappointments over the past years. There are still uncertainties with regard to the kinds of mobile services users want and need. We argue that users wants and needs depend on their context, which means that users should play an important role in the design process of mobile information services, through a structured approach in which developers and users work together. In this paper, we present a group-based approach to include the user early on in the design process in an efficient way. We have applied the group-based approach in three cases, i.e. mobile services for campus visitors, wireless applications for the process industry and services for crisis management. In all cases, involving users early on in the design process enabled the developers to gather useful information for designing mobile information services.     

Understanding and measuring the urban pervasive infrastructure

The increasing popularity of mobile computing devices has allowed for new research and application areas. Specifically, urban areas exhibit an elevated concentration of such devices enabling potential ad-hoc co-operation and sharing of resources among citizens. Here, we argue that people, architecture and technology together provide the infrastructure for these applications and an understanding of this infrastructure is important for effective design and development. We focus on describing the metrics for describing this infrastructure and elaborate on a set of observation, analysis and simulation methods for capturing, deriving and utilising those metrics.

Understanding and predicting students' intention to use mobile cloud storage services

The challenges of mobile devices such as limited bandwidth, computing, and storage have led manufacturers and service providers to develop new value-added mobile services. To address these limitations, mobile cloud computing, which offers on-demand services including platforms, infrastructure, and software have been developed. This study attempts to build a significantly improved research framework based on the Technology Acceptance Model in order to identify factors that affect students' attitudes toward and intentions in using mobile cloud storage services. A structural equation model was used to assess the proposed model based on the data collected from 262 undergraduate students. Results show that perceived usefulness, subjective norm, and trust have a significantly positive effect on the attitude, which in turn is a significant predictor of behavioral intentions. The research model, which explains 82% of the variance in attitudes toward using mobile cloud storage services has a strong predictive power. The findings have both theoretical and practical implications for academics, managers, and educational institutions.     

Joint contexts optimization for mobile grid

This paper presents joint contexts optimization in mobile grid. The paper describes device context information for context-aware services in the mobile device collaboration. The objective of the paper is to dynamically deliver services to mobile grid users according to current context of mobile grid environment. A utility function is used as objective function that expresses values for the current contexts. The optimization is carried out by the joint context parameter optimizer with respect to an objective function. A joint contexts optimization algorithm is proposed which decomposes mobile grid system optimization problem into sub-problems. In the experiment, the performance evaluation of joint contexts optimization algorithm is conducted.     

The ECORA framework: A hybrid architecture for context-oriented pervasive computing

An infrastructure approach to support context-aware pervasive computing is advantageous for rapid prototyping of context-aware distributed applications and beneficial for unifying modelling of context and reasoning in uncertain conditions. This paper presents the ECORA framework for context-aware computing, which is designed with a focus on reasoning about context under uncertainty and addressing issues of heterogeneity, scalability, communication and usability. The framework follows an agent-oriented hybrid approach, combining centralized reasoning services with context-aware, reasoning capable mobile software agents. The use of a centralized reasoning engine provides powerful reasoning capabilities and deploying context-aware mobile agents enables agility and robustness of components in the pervasive system. The design and implementation of the framework at different levels, as well as three case studies, are presented.     

Evaluation of mobile cloud architectures

The progress of mobile cloud computing is currently facing a crossroad on whether to implement user-side tools for job offloading or adopt network-side architecture. Selecting the best mobile cloud architecture is vital for having clear decisions on the future of mobile cloud computing.This work will survey mobile cloud architectures and compare their performance against existing resource demanding applications. The comparison will be performed using physical implementation. To the best of our knowledge, this paper is the first published work numerically comparing mobile cloud architectures across various mobile cloud applications.     

移动计算中移动性对Internet各层的影响

在移动计算中,移动性及其相关的无线环境特点给Internet网络协议提出了新的挑战,该文分析了移动性对Internet中物理和链路层、网络层、传输层、应用层的影响,并介绍了目前上述各层中的主要解决方案,综合地分析了各类解决方案的优劣,提出了一个多层协作的移动性支持的机制.     

移动社交网络环境下的真实社会关系估计

移动设备的普及促进了移动社会网络的形成。移动社会网络基于用户的物理特征为其提供虚拟交互,而用户在真实世界中的社会关系知识可有效地用于改善移动社会网络服务质量。提出一种基于用户物理特征(包括由GPS坐标代表的位置特征和由蓝牙检测代表的邻近特征)估计其真实社会关系的方法。该方法首先基于用户的GPS轨迹挖掘语义化访问地点(如家、工作地点等),然后结合语义化访问地点和邻近特征估计用户间的社会关系类型。实验结果表明该方法可准确估计三种类型的真实社会关系(包括家人、同事和朋友)。     

Understanding contexts by being there: case studies in bodystorming

A thorough appreciation of physical, social, interactional, and psychological contextual factors is crucial in the design of ubiquitous computing applications. This paper investigates the benefits of a method called bodystorming for carrying out design sessions in the original context, `in the wild', instead of the office. A location is selected that is identical or similar to the original environment. Innovation, carried out on-site, is based on ethnographical data presented as concrete design questions. Individual solutions to design questions are brainstormed and discussed on-site. Facets of data collection and preparation, formulation of design questions, selection of locations, session administration, and evaluation of design ideas are presented. We found that bodystorming permits immediate feedback for generated design ideas, and can provide a more accurate understanding of contextual factors. Bodystorming sessions were found memorable and inspiring. It is best suitable for designing for activities that are accessible and unfamiliar to the researchers.     

Improving the match between callers and receivers: A study on the effect of contextual information on cell phone interruptions

A problem with the location-free nature of cell phones is that callers have difficulty predicting receivers' states, leading to inappropriate calls. One promising solution involves helping callers decide when to interrupt by providing them contextual information about receivers. We tested the effectiveness of different kinds of contextual information by measuring the degree of agreement between receivers' desires and callers' decisions. In a simulation, five groups of participants played the role of ‘Callers’, choosing between making calls or leaving messages, and a sixth group played the role of ‘Receivers’, choosing between receiving calls or receiving messages. Callers were provided different contextual information about Receivers' locations, their cell phones' ringer state, the presence of others, or no information at all. Callers provided with contextual information made significantly more accurate decisions than those without it. Our results suggest that different contextual information generates different kinds of improvements: more appropriate interruptions or better avoidance of inappropriate interruptions. We discuss the results and implications for practice in the light of other important considerations, such as privacy and technological simplicity.     

Improving the match between callers and receivers: A study on the effect of contextual information on cell phone interruptions

A problem with the location-free nature of cell phones is that callers have difficulty predicting receivers' states, leading to inappropriate calls. One promising solution involves helping callers decide when to interrupt by providing them contextual information about receivers. We tested the effectiveness of different kinds of contextual information by measuring the degree of agreement between receivers' desires and callers' decisions. In a simulation, five groups of participants played the role of 'Callers', choosing between making calls or leaving messages, and a sixth group played the role of 'Receivers', choosing between receiving calls or receiving messages. Callers were provided different contextual information about Receivers' locations, their cell phones' ringer state, the presence of others, or no information at all. Callers provided with contextual information made significantly more accurate decisions than those without it. Our results suggest that different contextual information generates different kinds of improvements: more appropriate interruptions or better avoidance of inappropriate interruptions. We discuss the results and implications for practice in the light of other important considerations, such as privacy and technological simplicity.     

普适计算环境下基于中间件的上下文质量管理框架研究

随着信息技术的快速发展,分布式计算技术逐渐向普适计算技术演化,从而达到信息空间和物理空间融合的最终目标,为用户提供普适的智能化服务。为了达到这个目标,一个主要的困难就是如何有效地连续监测、才甫获与解释环境相关的上下文信息来确保精确的上下文感知性。很多研究者已先后投身于上下文感知的普适应用的研究工作中,但大多数往往直接针对原始上下文进行处理,没有考虑上下文质量(QoC)的影响。因此,提出了一种基于中间件的上下文质量管理框架,即通过上下文的质量门阂管理、重复与不一致的上下文丢弃等不同层次的控制机制,为上下文感知服务和应用用户提供有效而可靠的上下文服务。