Mobile input methods (IMEs) for text entry in interactive applications, are typically evaluated in lab settings, using phrase transcription tasks as the de-facto procedural element in the validation stage of their development. Transcription tasks offer strong internal validity but weak ecological and external validity, due to the composition constraints imposed on participants. Free composition tasks using image stimuli have been proposed as an alternative, but they lack standardized control to regulate elicited text volume and quality, therefore limiting evaluation internal validity. In this paper, we propose a methodology for rigorous, computational sampling of image stimuli from large image datasets, with an aim to control lexical and semantic similarity in user-generated text during IME evaluations. We further deploy diffusion generative AI models to methodically derive stylistic variations from the sampled images, allowing us to examine the effects of original images, abstractive styles and distractor elements on user input. Our findings from an online image description study with crowdsourced participants ( N = 100) and 3,000 captured input samples, demonstrate that stimulus sampling and restyling can be used a methodological control apparatus for evaluating input methods in lab settings, allowing researchers to systematically control participants’ input density and diversity, mitigating the internal validity challenges of image task evaluations. We present evidence-based guidelines for selecting image stimuli and release our datasets, experiment application, analysis code, and participant descriptions.

Typing on mobile soft keyboards is an acquired skill that users learn through experience. Previous research has modelled learning of keyboard layouts via statistical approximation of the probability of correct recall of a target’s (key) location from long and short-term memory, however, there are no insights as to how the mental model of the keyboard may be formed inside the brain. We construct a theory that could explain this process sufficiently, highlighting the importance of mental landmarks for efficient storage and recall of spatial information. The theory is explored and validated through simulation of a cognitive architecture and comparison with extant empirical data, generating insights that could inform the design of new layouts and facilitate the learning process for novice users.

Mobile text entry for sighted and blind persons has received much research attention. However, much less is known about meeting the text entry needs of persons with low vision, whose ability to use the visual channel alongside audio, speech and haptic modalities, may open unexplored opportunities for efficient and privacy-preserving mobile text entry. We present findings from a qualitative study with 9 low vision users, revealing current text entry challenges for this user group, and providing future directions for text entry research.

Predicting the footfall in a new brick-and-mortar shop (and thus, its prosperity), is a problem of strategic importance in business. Few previous attempts have been made to address this problem in the context of big data analytics in smart cities. These works propose the use of social network check-ins as a proxy for business popularity, concentrating however only on singular business types. Adding to the existing literature, we mine a large dataset of high temporal granularity check-in data for two medium-sized cities in Southern and Northern Europe, with the aim to predict the evolution of check-ins of new businesses of any type, from the moment that they appear in a social network. We propose and analyze the performance of three algorithms for the dynamic identification of suitable neighbouring businesses, whose data can be used to predict the evolution of a new business. Our SmartGrid algorithm reaches a performance of being able to accurately predict the evolution of 86% of new businesses.

Smartphone notifications are a major source of interaction with mobile devices. In this paper we address a gap in literature by establishing a foundation that explains the role of modalities with which a notification is delivered on a mobile device. Though previous studies have attempted to address this question, we find that they suffer from significant internal validity problems. As such we conducted an ecologically valid and carefully designed experiment in a controlled environment that simulates a smart home environment. Our work extends into smart environments, by examining a new modality, implemented by pairing the smartphone to a connected lighting system and replicating mobile notifications to smart light bulbs in the user's field of vision. We derive a set of guidelines for choosing notification modalities and set future research directions.

Multistage Interconnection Networks (MINs) remain interesting for research and are continuously being improved as they are essential devices for constructing scalable parallel computers or for connecting networks. In this paper a new idea - new architecture - is introduced. The proposed construction uses switch elements connected with redundancy internal paths and fan out at the end of the construction. In this multistage system, the performance metrics in terms of throughput and packet latency are improved and the fault tolerance is kept within acceptable limits. Moreover, we demonstrate that the cost of the proposed innovative fabric is not expensive compared to other similar switching structures in terms of network size. The amelioration of the proposed system is demonstrated quantitatively.

Location based services are a common application scenario in mobile and ubiquitous computing use. A typical issue with cartographic applications in this domain is the limited size of the displayed map, which makes interaction and visualization a difficult problem to solve. With the increasing popularity of head mounted displays for VR and AR systems, an opportunity is presented for map-based applications to overcome the limitation of the small display size, as the user's information visualization space can extend to his entire surroundings. In this paper we present a preliminary investigation into how interaction with such very large display maps can take place, using a virtual reality headset as the sole input and interaction method.

Equipping an imaginary Random Surfer of the Web with the ability to teleport, was Page et al.'s creative way to justify a mathematical necessity; the Teleportation Matrix. Despite being essential for ensuring the ergodicity of the underlying Markov chain, the standard definition of this matrix treats the nodes of the graph in a simplistic and “leveling” way that can prove counterintuitive - especially for applications of the method on graphs of heterogeneous data. In this work, we focus on such graphs and we propose a novel alternative teleportation model that yields a well-defined ranking vector, while being as easy to handle as the traditional teleportation. We explore the theoretical implications of our model, and we reveal a wealth of nice properties that result to direct computational advantages over PageRank. We conduct a set of experiments using real-world datasets and we verify both the useful computational characteristics of our model and its favorable qualitative performance. Our promising findings suggest there remain more to be explored, and maybe much to be gained, by revisiting the teleportation model; a neglected part of PageRank that is typically taken for granted by the majority of applications in the literature.

The automatic analysis of legislative texts using Natural Language Processing techniques is able to facilitate several tasks related to the legislation lifecycle, such as the consolidation of different versions of legal documents. We present our work on the automatic identification, extraction and application of textual amendments in Greek legislative texts, based on pattern matching with regular expressions, which is part of a semi-automatic system for the consolidation of Greek laws.

Making recommendations in the presence of sparsity is known to present one of the most challenging problems faced by collaborative filtering methods. In this work we tackle this problem by exploiting the innately hierarchical structure of the item space following an approach inspired by the theory of Decomposability. We view the itemspace as a Nearly Decomposable system and we define blocks of closely related elements and corresponding indirect proximity components. We study the theoretical properties of the decomposition and we derive sufficient conditions that guarantee full item space coverage even in cold-start recommendation scenarios. A comprehensive set of experiments on the MovieLens and the Yahoo!R2Music datasets, using several widely applied performance metrics, support our model’s theoretically predicted properties and verify that NCDREC outperforms several state-of-the-art algorithms, in terms of recommendation accuracy, diversity and sparseness insensitivity.

Location sharing services can be seen as "social sensors" that provide data revealing real world interactions. In this paper, we examine the case of foursquare check-ins at airports and we show that these data can be indicative of the passengers’ traffic, while their number is hundreds of times lowe

As typical turn by turn systems fail in several aspects to provide an engaging experience to pedestrians in urban environments, we investigate the potential of alternative interaction methods for navigation. We present a two-phase experiment, involving both audio and tactile navigation and discuss the collected evaluation data. Our findings show a positive reception of implicit navigation from our users.

We describe our analysis of three months worth of collected human-physical environment interactions (foursquare check-in) data for two European cities: a medium-sized city in the Mediterranean and a larger city in North West Europe. Our analysis shows that though the data generated by the citizens is scarce (i.e. on average less than 15 users checked in at any time during the day), nevertheless they can closely reflect a city's dynamics. The paper also discusses the strong suggestion of emergent cultural traits from the data and its use to power new pervasive applications based on human-physical interaction.

Our work discusses a mobile contact retrieval interface which attempts to contextually predict the contacts a user is likely to need access to, in order to facilitate the retrieval process. We compare our prototype implementation with retrieval from traditional applications (contact list and call log) in a preliminary lab experiment and discuss our findings from user behaviour. We conclude with suggestions on how to improve this interface in order to further enhance the retrieval process.

In this paper we present HotCity, a service that demonstrates how collecting and mining the interactions that users make with the urban environment through social networks, can help tourists better plan activities, through sharing the collectively generated social context of a smart, connected city, as a background layer to mapped POI. The data for our service stems from the collection and analysis of 1-month worth of collected human-physical environment interactions (i.e., Foursquare check-ins) data for Oulu, a medium-sized city in Finland, where our service is deployed in ubiquitous public displays. Our analysis demonstrates that a good model of the city's dynamics can be built despite the low popularity of Foursquare amongst locals. Our findings from the field-based trial of the HotCity service yield several useful insights and important contributions. We found that the method of using a heatmap as an intermediate layer of environmental context does not negatively affect the experience of users at the cognitive level, compared with a more traditional map and POI type of interface, where temporal aspects of context are not present. In the concluding sections, we discuss how this cloud-based service can also be used in a variety of ubiquitous computing platforms.

Research about the topological characteristics of the hyperlink graph has shown that Web possesses a nested block structure, indicative of its innate hierarchical organization. This crucial observation opens the way for new approaches that can usefully regard Web as a Nearly Completely Decomposable(NCD) system; In recent years, such approaches gave birth to various efficient methods and algorithms that exploit NCD from a computational point of view and manage to considerably accelerate the extraction of the PageRank vector. However, very little have been done towards the qualitative exploitation of NCD.

In this paper we propose a system for localization in a Wi-Fi environment where the exported information is used in m-commerce applications [2–4] via techniques of data mining [29,31]. The system uses the map of the field of interest and by preprocessing it, extracts a graph of the positions a user can be, along with the possible transitions between these positions. This map is used for the localization process along with the particle filtering [11] Monte Carlo technique, which attempts to extract the noise from the measurements collected during the process. In addition to this we apply novel inside-the-particle-filtering-process techniques and propose a computational system that listens to the wireless environment in order to augment the overall system’s performance. Having the extracted positioning information, m-commerce targeted messages are sent to the users. Additionally, the spatio-temporal data are processed by data mining techniques in order to export the correlations between the users’ locations.

Contact lists are one of the most frequently used applications on mobile devices. Users are reluctant to delete or remove contacts from their repositories and as modern smartphones provide an unlimited contact list storage space, these become increasingly large, sometimes measuring several hundred entries. In this paper we present our findings from two experiments with user-subjective and quantitative data concerning the use of mobile contact lists. We examine the role that frequency and recency of usage plays in the determination of a contact's importance, with a view to aid the speed and efficacy of the information seeking and retrieval process during the use of the contact list application.

We propose the application of a dimensionality reduction algorithm that could provide a breakthrough in the efforts to retrieve and present mobile personal information to the user in context.

Context-aware ubiquitous computing applications thrive in extremely dynamic and heterogeneous environments. When they are delivered to the user preconfigured and without the capability to be adapted, they may fail to satisfy the user's changing needs and may give the user the feeling that control is taken away from him. In this paper we present how context can be exploited in ubiquitous computing environments in order to enable the user to setup his own application. We will focus on how context can be modelled using ontologies, on the management of accumulated context data and on the reasoning process based on intelligent context and rules defined by the user.

Many companies today are providing customer services via the Web and the telephone. Demand for providing Web data in audio form is increasing every day. Voice response facilities are used for various kinds of information over the phone: time, weather, horoscopes, lottery results, sports events, news, etc. VoiceXML is an enabling technology for creating a streamlined speech-based interface for web-based information services. Speech technology, as it improves, will become a very natural and powerful interface for ubiquitous access to information. Moreover, VoiceXML applications are available through computers or through the telephone, which is a universal means of communication. In this paper, we describe a dynamic speech-enabled system powered by VoiceXML in which the available information is dynamically generated by PHP.

Mobile commerce (m-commerce) is a rather new field in the business world. It depends on wireless networks for accessing the Internet from mobile devices and for exchanging data between such devices. Wireless technologies on the one hand evolve rapidly and are met in many different applications. On the other hand a plethora of factors encourage market to make advances towards the m-commerce market. New ideas about m-commerce services and applications find acceptance by the business world and by users. Unfortunately not all users know how to create m-commerce services and applications. Thus a system which can easily create mobile commerce systems can be proved very helpful. In this paper we present a system which can create other m-commerce systems in a user friendly way. The system is meant to be used in the m-commerce market as a mean of developing hotel Websites and mobile sites. It uses a simple form which guides the user to create fully functional websites and mobile sites. We focus on implementation issues and evaluate our system after testing it. Finally, conclusions are extracted and future work is proposed.

As mobile devices are becoming increasingly powerful and ubiquitous, new possibilities to get route guidance are created, allowing users to save valuable time and effort. However, mobile devices still face severe constraints that limit the possibilities that a mobile route finding application may offer. In this paper, we present a device independent mobile application that enables mobile users to receive route directions to their handheld device. This application is an extension to an existing mobile map delivery system, the m-CHARTIS system. We focus on the main features and we analyse the device independent character of the application. Implementation details are presented and finally directions for future work are proposed.

In this work, we introduce metrics and a proposed procedure to measure the popularity of a website. We present two novel metrics, Promo and Promo(2) that take advantage of the internal link structure of a website, in order to gain important navigation information. This is indicative of the difficulty the user encounters to access a particular link and can be combined with statistics gained from the log files as a metric of popularity. The two metrics propose a different definition of the popularity of a web object in order to generate a sorted list of promotion values for a website's links. We have delivered a web tool that implements the proposed procedure in order to facilitate a site designer to manipulate his/her web server log data, receive recommendations and popularity results and finally proceed with changes in the structure or position of links. Overall, the experimental study using user-based accesses log data, has been encouraging and it has verified the effectiveness of the Promo metrics.

Nowadays, the rapid growth of mobile devices and mobile applications has changed the way we live. Mobile devices are widely used and they are providing people with needed information anytime and anywhere. People use mobile applications in many ways, for business purposes, as an organizer or even for entertainment. The development of mobile applications needs to be adapted with the special features and limitations of these devices. Looking in this direction, we present a mobile map application that we have developed for Microsoft Windows mobile users, which is using geographic data stored in the device's memory and allows the user to navigate through the map of different cities. A special feature of our application is the simulation of a classic map by giving the user the opportunity to take notes and marks on the map by clicking on the device's screen. These data are stored in the device and based on them we propose some ways to make navigation in mobile map applications faster and easier.

A map is one of the most useful media in disseminating spatial information. As mobile devices are becoming increasingly powerful and ubiquitous, new possibilities to access map information are created. However, mobile devices still face severe constraints that limit the possibilities that a mobile map application may offer. We present the m-CHARTIS system, a device independent mobile map application that enables mobile users to access map information from their device.

Describes a system offering a solution to the problem of ambulance management and emergency incident handling in the prefecture of Attica in Greece. It is based on a geographic information system (GIS) coupled with GPS (Global Positioning System) and GSM (Global System for Mobile Communication) technologies. The system's operation is expected to minimize the ambulances' response time. Consequently, there will be a drastic improvement in the way emergency incidents are being handled. This fact will thus significantly affect the quality of health services offered to citizens.

The growth of networked systems has magnified the use of raw resources such as images, animations, videos, etc. The networking facilities between different systems and the lack of security between them have introduced the need for image, animation and video copyright protection. One approach used to address this problem is the use of structure that can seal or mark any digital material. These structures are called watermarks. In this paper, we present different solutions, commercial, freeware or scientific, for the marking of multimedia objects.

Multistage interconnection networks with crossbar switches are a major component of parallel machines. In this paper we analyze Banyan networks of k by k switches and with finite buffers. The exact solution of the steady state distribution of the first stage is derived in the situation where packets are lost when they encounter a full buffer (Assumption A). The solution is a linear combination of k-1 geometrics. We use this to get an approximation for the steady state distributions in the second stage and beyond. As a side effect, the infinite buffer case is solved, confirming known results. Our results are validated by extensive simulations. An alternate situation of networks where full buffers may block previous switches is also analyzed through an approximation technique (Assumption B).

Our work deals with the analysis of the queueing delays of buffered multistage Banyan networks of multiprocessors. We provide tight upper bounds on the mean delays of the second stage and beyond, in the case of infinite buffers. Our results are validated by simulations performed on a network simulator constructed by us. The analytic work for network stages beyond the first, provides a partial answer to open problems posed by previous research.