Mobile guides: Taxonomy of architectures, context awareness, technologies and applications
Journal of Network and Computer Applications
Portable devices are increasingly employed in a wide range of mobile guidance applications. Typical examples are guides in urban areas, museum guides, and exhibition space aids. The demand is for the delivery of context-specific services, wherein the context is typically identified by a combination of data related to location, time, user profile, device profile, network conditions and usage scenario. A context-aware mobile guide is intended to provide guidance services adjusted to the context
... the received request. The adjustment may refer to tailoring the user interface to the perceived context, as well as delivering the right type of information to the right person at the right time and the right location. It may also refer to intermediary adaptation, as in the case of mobile multimedia transmission. This paper offers a taxonomy of mobile guides considering multiple criteria. The taxonomy considers several aspects of the mobile applications space, including context awareness, client architectures, mobile user interfaces, as well as offered functionalities, highlighting functional, architectural, technological, and implementation issues. Existing implementations are classified accordingly and a discussion of research issues and emerging trends is offered. , ELSEVIER 3 location  . Although context-dependent delivery can be relevant to non-mobile applications too, the flexibility offered by the device and user mobility places mobile applications at the very heart of context-aware computing [38, 99] . Furthermore, as mobile devices and tools are being increasingly employed in collaborative settings, the prospect of true mobile collaboration is raising expectations for deeper business penetration of mobile guides. Such expectations are supported by the emerging characteristics of mobile applications, including active data management, enhanced web-based interactivity, ready access to knowledge and information, and usage of advanced communication networks  . Mobile guides provide context-dependent, multimedia-rich touring services for visitors. A typical simple scenario is that of a user operating a portable computing device, e.g. a Personal Digital Assistant (PDA) or a smartphone, in order to get interactive indoors or outdoors navigation aid. However, mobile guide functionalities offered today cover a much wider range of activities. These include navigation services (via location-awareness and map-based navigation) , access to additional services (bookmarking, collaboration, shopping, email, data processing), contextual information delivery with multimedia (video delivery, educational tools and games) and in some cases annotation options and user provided content, as well as advanced knowledge processing resulting in adaptive and context-dependent services. Knowledge deduced from user data can be exploited to tailor the offered services and content to the user profile and offer better recommendations for available tasks and services. In this paper we provide an analysis and taxonomy of the mobile guides' literature by considering multiple criteria, to accommodate for the considerable complexity of the mobile guides application space. Previous surveys focused largely on context awareness [86, 98] or location estimation [12, 68] . In  an evaluation framework for mobile guides is developed and four representative mobile guides are evaluated. A requirement assessment of mobile tourism services is provided in  , both from the tourists' and the service operators' perspectives. In  a survey is performed taking into account several technological axes (localization, networking, input/output systems and provided services) and examining a limited number of systems in detail. Our survey acknowledges the complexity of the mobile space  and therefore follows a review methodology that seeks to take it into account in a comprehensive manner. This paper is structured as follows. In Section 2 we present our review analysis methodology, explaining the methodology for application selection, as well as the taxonomy axes selected. Section 3 contextualizes our research by providing an overview of the mobile guide applications, highlighting the functionalities that mobile guides are offering. Before analyzing the mobile guide taxonomy and literature, Section 0 provides an analysis of the key concept of context and context aware services, along with an updated classification of context categories, to suit the mobile guide domain. Section 5 presents the detailed literature taxonomy, classifying and analyzing relevant literature accordingly. The paper closes with a discussion on the current trends, including a research outlook for future research & development in the area of mobile guides. Review Analysis Methodology Research methodology in mobile guides is severely constrained by the level of fragmentation and complexity of the 'mobile space' itself. In particular, the multiple factors contributing to this complexity include the variety of users, the different characteristics of the employed hardware devices, the nature of the software development and execution platforms, the diversity of the delivered content, the multitude of networking delivery means, along with associated delivery bandwidth, the increasing impact of context-awareness, as well as the actual functionality offered by mobile applications  . Thus, in contrast with previous surveys, this paper seeks to take into account all aforementioned issues related to the complexity of the mobile space, focusing on technical aspects of mobile guide development, offered functionalities and services availability and delivery, as well as considering networking and user interface issues, highlighting functional, architectural, technological, and implementation issues. We discuss, analyze and categorize the literature taking into account multiple such criteria, which differentiate the various implementations and constitute important aspects of design and system development. While past surveys focus on a limited set of such criteria, a more comprehensive treatment and taxonomy of mobile guidance literature has been missing. Therefore, our comprehensive literature classification, apart from reviewing the offered functionalities, it further analyzes implementations under the two broad taxonomy axes shown in Fig. 1. A. System Technologies and Characteristics. 1. Localization techniques, i.e. how user location and/or orientation are inferred. 2. Environment type (e.g. indoors/outdoors). 3. Data retrieval (e.g. means of data delivery to the device).