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International audience; Domain-Specific Languages (DSLs) manifest themselves in remarkably diverse shapes, ranging from internal DSLs embedded as a mere fluent API within a programming language, to external DSLs with dedicated syntax and tool support. Although different shapes have different pros and cons, combining them for a single language is problematic: language designers usually commit to a particular shape early in the design process, and it is hard to reconsider this choice later. In this new ideas paper, we envision a language engineering approach enabling (i) language users to manipulate language constructs in the most appropriate shape according to the task at hand, and (ii) language designers to combine the strengths of different technologies for a single DSL. We report on early experiments and lessons learned building Prism, our prototype approach to this problem. We illustrate its applicability in the engineering of a simple shape-diverse DSL implemented conjointly in Rascal, EMF, and Java. We hope that our initial contribution will raise the awareness of the community and encourage future research.

Logarithmic number systems (LNS) reduce hardware complexity for multiplication and division in embedded systems, at the cost of more complicated addition and subtraction. Existing LNS typically use base-2, meaning that representable numbers are some (often fractional) power of two. We argue that other bases should be considered. The base of the LNS determines the distribution of values and may reduce representation errors when converting inputs to LNS in domain-specific embedded hardware accelerators. Further, LNS addition and subtraction are normally implemented with lookup tables whose properties may be a function of the base. We show that other bases can lower both representation and addition and subtraction error. We consider the case of 8-bit LNS, when converting from 8-bit floating point (FP). We find that base-1.984 significantly reduces the conversion error. Where we can scale values, base-1.851 reduces the error to just 0.011 units of least precision (ULP). A suitable base can also reduce average arithmetic errors. For example, base-1.802 LNS has an average error of 0.242 ULP and 0.212 ULP as compared to 0.243 ULP and 0.226 ULP for addition and subtraction, respectively, for base-2.

Misinformation has become a common part of our digital media environments and it is compromising the ability of our societies to form informed opinions. It generates misperceptions, which have affected the decision making processes in many domains, including economy, health, environment, and elections, among others. Misinformation and its generation, propagation, impact, and management is being studied through a variety of lenses (computer science, social science, journalism, psychology, etc.) since it widely affects multiple aspects of society. In this paper we analyse the phenomenon of misinformation from a technological point of view. We study the current socio-technical advancements towards addressing the problem, identify some of the key limitations of current technologies, and propose some ideas to target such limitations. The goal of this position paper is to reflect on the current state of the art and to stimulate discussions on the future design and development of algorithms, methodologies, and applications.

To preserve high quality of a project, it is necessary to perform many refactoring steps during the development and maintenance phases. Code refactoring received a great attention in the literature, often directed to the refactoring of code smells. While at the architectural level, architectural smells received less attention. One of the most common architectural smell which may affect many parts of a software application is the Cyclic Dependency smell. This position paper presents a tool prototype that suggests which path a developer could follow to remove Cyclic Dependency smells in Java applications. The tool has been developed as an extension of the Arcan tool for architectural smells detection. In this paper we describe how the tool identifies the path to follow for the refactoring of Cyclic Dependency on real projects. The tool has been thought only to suggest a possible refactoring approach which a developer could considerate to resolve Cyclic Dependency.

This position paper describes how blockchains facilitate the implementation of distributed self-adaptive systems. We demonstrate how the master/slave decentralised control pattern for self-adaptive systems, integrated with a permissioned blockchain, can protect nodes of a network against attacks by continuously adapting the membership of an access control list. Whenever malicious behaviour is detected, consensus on an updated access control list is reached, and that node is removed from the network. Using a smart home, as an example, we demonstrate that a permissioned blockchain is able to maintain a consistent view of a network of Internet of Things (IoT) devices in the presence of malicious nodes.

International audience; A heterogeneous network, where a switched-Ethernet backbone, e.g. AFDX, interconnects several end systems based on Network-on-Chip (NoC), is a promising candidate to build new avionics architectures. When using such a heterogeneous network for real-time applications, a global worst-case traversal time (WCTT) analysis is needed. In this short paper we focus on the intra-NoC communication on a Tilera TILE64-like NoC. First, we extend the Recursive Calculus (RC) to achieve tighter intra-NoC WCTT. Then, we explain how this intra-NoC WCTT analysis could be used in a compositional manner for the end-to-end inter-NoC delay analysis.

This workshop aims at discussing the rich possibilities that the body offers to experience the external world and the prospects that arise for interaction designers when these often-neglected abilities are taken into account. In particular, the workshop will focus on the rediscovery of the five senses, either alone or in a multimodal combination, and of the perceptual-motor abilities of our body. The one-day workshop is divided in two steps: first, participants will have the possibility to briefly present and discuss with the other attendees their research. Workshop candidates are requested to send a position paper, including a short biography and detailing their research interests and background. Second, participants will have the possibilities to explore and rediscover their sensorimotor abilities through several exercises and games abilities using a critical design approach. Interdisciplinary groups will be challenged to design and develop new interaction experience concepts using our natural 'tools' as prototyping tools.

We present the design of the first prototype of TOK - a tangible interface for children to create their own stories. Based on data collected with two groups of five years old preschoolers we present our findings regarding the interaction design of the system. The picture cards have shown to generate ideas, acting as input for the creation of stories, promoting creativity while proposing a framework that supports and guides the construction of logical structures. This is a first step in an effort to build a toolkit of tangible interfaces allowing children and teachers to build their own digital enhanced learning activities., FCT-QREN-COMPETE-UE

This day-long workshop aims to support and grow the community of CSCW and NCI scholars that investigate the past to inform the design, critique and conceptualization of technology. At this workshop, we will learn from examples of historically-based CSCW and HCI work, explore issues in historical method that come up in such work, share methods and techniques, provide feedback and support to ongoing investigations; and define a shared agenda for future research on this topic. The workshop will also highlight research and methods that focus on non-Western contexts and that give voice to historically marginalized groups. Based on the workshop, we will develop a white paper and a website that will collect resources to support CSCW based historical investigations.

This paper argues that a significant paradigm change in contemporary dance can offer further opportunities for HCI researchers interested in embodied interaction and interactive system design. Based on the analysis of 42 HCI papers in our data set, resulting from searches in two computing research libraries, we suggest seven thematic categories that reflect how HCI researchers have been engaging with contemporary dance. Moreover, we propose a standardized usage of contemporary dance terminology in HCI literature, and discuss the current state of engagement with publications from the field of performance theory. We identify three opportunities for HCI, which can arise through further engagement with the knowledge produced in contemporary dance and performance: to engage with the field of embodied interaction from the perspective of performance research and theory; to employ contemporary dance methods and practices in HCI research; and to integrate contemporary dance choreographers and performers as researchers in interdisciplinary projects.

The recent European General Data Protection Regulation (GDPR) and other data protection regulations restrict the processing of some categories of personal data (health, political orientation, sexual preferences, religious beliefs, ethnic origin, etc.) due to the privacy risks associated to such information. The GDPR refers to these categories as sensitive personal data. This paper quantifies the portion of Facebook (FB) users, across 197 countries, who are labeled with advertising interests linked to potentially sensitive personal data. Our study reveals that Facebook labels 67% of users with potential sensitive interests. This corresponds to 22% of the population in the referred 197 countries. Moreover, our work shows that the GDPR enforcement had a negligible impact in this context since the portion of FB users labeled with sensitive interests in the European Union remains almost the same 5 months before and 9 months after the GDPR was enacted. The paper also illustrates potential risks associated to the use of sensitive interests. For instance, we quantify the portion of FB users labelled with the interest "Homosexuality" in countries where being gay may be punished with the death penalty. The last contribution is the implementation of a web browser extension that allows FB users removing in a simple way the potentially sensitive interests FB has assigned them.

© 2020 Association for Computing Machinery. In indexing a graph for distance queries, distance labeling is a common practice; in particular, 2-hop labeling which guarantees the exactness of the query results is widely adopted. When it comes to a massive real graph with a relatively large treewidth such as social networks and web graphs, however, 2-hop labeling can hardly be constructed due to the oversized index. This paper discloses the theoretical relationships between the graph treewidth and 2-hop labeling's index size and query time. To scale up distance labeling, this paper proposes Core-Tree (CT) Index to facilitate a critical and effective trade-off between the index size and query time. The reduced index size enables CT-Index to handle massive graphs that no existing approaches can process while the cost in the query time is negligible: the query time is below 0.4 milliseconds on all tested graphs including one graph with 5.5 billion edges.

This paper provides an overview of our open Ultra Video Group (UVG) dataset that is composed of 16 versatile 4K (3840×2160) test video sequences. These natural sequences were captured either at 50 or 120 frames per second (fps) and stored online in raw 8-bit and 10-bit 4:2:0 YUV formats. The dataset is published on our website (ultravideo.cs.tut.fi) under a non-commercial Creative Commons BY-NC license. In this paper, all UVG sequences are described in detail and characterized by their spatial and temporal perceptual information, rate-distortion behavior, and coding complexity with the latest HEVC/H.265 and VVC/H.266 reference video codecs. The proposed dataset is the first to provide complementary 4K sequences up to 120 fps and is therefore particularly valuable for cutting-edge multimedia applications. Our evaluations also show that it comprehensively complements the existing 4K test set in VVC standardization, so we recommend including it in subjective and objective quality assessments of next-generation VVC codecs. acceptedVersion

In recent years, multiple public cloud FPGA providers have emerged, increasing interest in FPGA acceleration of cryptographic, bioinformatic, financial, and machine learning algorithms. To help understand the security of the cloud FPGA infrastructures, this paper focuses on a fundamental question of understanding what an adversary can learn about the cloud FPGA infrastructure itself, without attacking it or damaging it. In particular, this work explores how unique features of FPGAs can be exploited to instantiate Physical Unclonable Functions (PUFs) that can distinguish between otherwise-identical FPGA boards. This paper specifically introduces the first method for identifying cloud FPGA instances by extracting a unique and stable FPGA fingerprint based on PUFs measured from the FPGA boards' DRAM modules. Experiments conducted on the Amazon Web Services (AWS) cloud reveal the probability of renting the same physical board more than once. Moreover, the experimental results show that hardware is not shared among f1.2xlarge, f1.4xlarge, and f1.16xlarge instance types. As the approach used does not violate any restrictions currently placed by Amazon, this paper also presents a set of defense mechanisms that can be added to existing countermeasures to mitigate users' attempts to fingerprint cloud FPGA infrastructures.

This paper details an experience report of two interventions which explored the use of a audience response system in summative assessment in two different ways within a con- version Masters degree programme. One course explored stu- dents understanding of topics and self-assessment of ability through small multiple-choice quizzes. The other course was based around cyber security and used the audience response system to ensure engagement with the pre-class reading material. Both interventions were designed in an attempt to encourage students to engage more effectively with the material. This paper aims to identify and contrast the ways in which the audience response system was used in assess- ment in higher education computing science with a view to suggesting key considerations for implementing such an intervention.

The concept of Capture the Flag (CTF) games for practicing cybersecurity skills is widespread in informal educational settings and leisure-time competitions. However, it is not much used in university courses. This paper summarizes our experience from using jeopardy CTF games as homework assignments in an introductory undergraduate course. Our analysis of data describing students' in-game actions and course performance revealed four aspects that should be addressed in the design of CTF tasks: scoring, scaffolding, plagiarism, and learning analytics capabilities of the used CTF platform. The paper addresses these aspects by sharing our recommendations. We believe that these recommendations are useful for cybersecurity instructors who consider using CTF games for assessment in university courses and developers of CTF game frameworks., ACM SIGCSE 2020 conference, 7 pages, 5 figures, 2 tables

This preprint follows ACM policy: “Authors who publish with ACM have the freedom to post peer-reviewed pre-print versions of their papers to personal websites and institutional repositories. They can add a single-click link to their final published papers, and re-use any portion of their published work with the inclusion of a citation and DOI link. Authors can also post on any repository legally mandated by the agency funding the research on which the work is based, and on any non-commercial repository or aggregation that does not duplicate ACM tables of contents/substantially duplicate an ACM-copyrighted volume or issue” (https://authors.acm.org/author-resources/author-rights.), Mental health e-coaches and technology-delivered services are showing considerable benefits to foster mental health literacy, monitor symptoms, favour self-management of different mental health conditions and scaffold positive behaviours. However, adherence to these systems is usually low and generally declines over time. There exists a recent body of work addressing engagement with mental health technology with the aim to understand the factors that influence sustained use and inform the design of systems that are able to generate sufficient engagement to attain their expected results. This paper explores the different facets of engagement in mental health e-coaches, including aspects related to the estimation of system use from log data, effective engagement, user experience, motivation, incentives, user expectations, peer support and the specific challenges of technologies addressed to mental health., This research has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 823907 (MENHIR project https://menhir-project.eu) and grant agreement No 769872 (EMPATHIC project http://www.empathic-project.eu).

Authors of academic papers are generally required to nominate several keywords that characterize the paper, but are rarely offered guidance on how to select those keywords. We analyzed the keywords in the past 15 years of selected computing education publications: the 1274 papers published in the proceedings of ICER and ITiCSE, including the ITiCSE working group reports. As well as the keywords assigned by the authors, we mined the abstracts of these papers to extract a separate list of keywords. Our work has two goals: to frame the thematic landscape of the field, using keywords that communicate the work conducted; and to detect differences between the human judgement and interpretation of keywords and the machine 'intelligence' on handling those keywords, with respect to the clusters of thematic topics identified in each case. The analysis shows that the field is dominated by learning approaches (e.g., active learning, collaborative learning), aspects of programming (e.g., debugging, misconceptions), computational thinking, feedback, and assessment, while other areas that have attracted attention include academic integrity (e.g., plagiarism) and diversity (e.g., female students, underrepresented groups). It was observed that the keywords chosen by authors are often too general to provide information about the paper (e.g., 'concerns', 'course', 'fun', 'justice'). We elaborate on the findings and begin a discussion on how authors can improve the communication of their research and make access to it more transparent. © ACM, 2020. This is the author's version of the work. It is posted here by permission of ACM for your personal use. Not for redistribution. The definitive version was published here, https://doi.org/10.1145/3372782.3406276

Augmented Reality (AR) based assistance has a huge potential in the context of Industry 4.0: AR links digital information to physical objects and processes in a mobile and, in the case of AR glasses, hands-free way. In most companies, order-picking is still done using paper lists. With the rapid development of AR hardware during the last years, the interest in digitizing picking processes using AR rises. AR-based guiding for picking tasks can reduce the time needed for visual search and reduce errors, such as wrongly picked items or false placements. Choosing the best guiding technique is a non-trivial task: Different environments bring their own inherent constraints and requirements. In the literature, many kinds of guiding techniques were proposed, but the majority of techniques were only compared to non-AR picking assistance. To reveal advantages and disadvantages of AR-based guiding techniques, the contribution of this paper is three-fold: First, an analysis of tasks and environments reveals requirements and constraints on attention guiding techniques which are condensed to a taxonomy of attention guiding techniques. Second, guiding techniques covering a range of approaches from the literature are evaluated in a large-scale picking environment with a focus on task performance and on factors as the users' feeling of autonomy and ergonomics. Finally, a 3D path-based guiding technique supporting multiple goals simultaneously in complex environments is proposed.

Vast numbers of publications in computing education begin with the premise that programming is hard to learn and hard to teach. Many papers note that failure rates in computing courses, and particularly in introductory programming courses, are higher than their institutions would like. Two distinct research projects in 2007 and 2014 concluded that average success rates in introductory programming courses world-wide were in the region of 67%, and a recent replication of the first project found an average pass rate of about 72%. The authors of those studies concluded that there was little evidence that failure rates in introductory programming were concerningly high. However, there is no absolute scale by which pass or failure rates are measured, so whether a failure rate is concerningly high will depend on what that rate is compared against. As computing is typically considered to be a STEM subject, this paper considers how pass rates for introductory programming courses compare with those for other introductory STEM courses. A comparison of this sort could prove useful in demonstrating whether the pass rates are comparatively low, and if so, how widespread such findings are. This paper is the report of an ITiCSE working group that gathered information on pass rates from several institutions to determine whether prior results can be confirmed, and conducted a detailed comparison of pass rates in introductory programming courses with pass rates in introductory courses in other STEM disciplines. The group found that pass rates in introductory programming courses appear to average about 75%; that there is some evidence that they sit at the low end of the range of pass rates in introductory STEM courses; and that pass rates both in introductory programming and in other introductory STEM courses appear to have remained fairly stable over the past five years. All of these findings must be regarded with some caution, for reasons that are explained in the paper. Despite the lack of evidence that pass rates are substantially lower than in other STEM courses, there is still scope to improve the pass rates of introductory programming courses, and future research should continue to investigate ways of improving student learning in introductory programming courses.

This paper reports on a co-speculative interview study with charitable donors to explore the future of programmable, conditional and data-driven donations. Responding to the rapid emergence of blockchain-based and AI-supported financial technologies, we specifically examine the potential of automated, third-party 'escrows', where donations are held before they are released or returned based on specified rules and conditions. To explore this we conducted pilot workshops with 9 participants and an interview study in which 14 further participants were asked about their experiences of donating money, and invited to co-speculate on a service for programmable giving. The study elicited how data-driven conditionality and automation could be leveraged to create novel donor experiences, however also illustrated the inherent tensions and challenges involved in giving programmatically. Reflecting on these findings, our paper contributes implications both for the design of programmable aid platforms, and the design of escrow-based financial services in general.

Network segmentation is a powerful tool for network defense. In contemporary complex, dynamic, and multilayer networks, network segmentation suffers from lack of visibility into processes in the network, which results in less strict segment definition and loosen network security. Moreover, the dynamics of the networks makes the manual identification of network segments nearly impossible. In this paper, we inspect the possibilities of the behavior-aware network segmentation using IP flows and machine learning approaches that would enable to identify segments automatically, even in a complex network. We evaluate the suitability of clustering algorithms for identification of behavior-consistent segments in a network. We show that the clustering algorithms can identify relevant behavior-consistent clusters that overlap with those identified manually by experts. Apart from the segment identification, we investigate the other essential task of network segmentation process: assignment of an unknown host to an existing segment. We evaluate the performance of four different classification mechanisms on a real-world dataset. We show that it is possible to assign an unknown host to an appropriate network segment with up to 92% precision. Moreover, we release the whole dataset and experiment steps available for public use. Network segmentation is a powerful tool for network defense. In contemporary complex, dynamic, and multilayer networks, network segmentation suffers from lack of visibility into processes in the network, which results in less strict segment definition and loosen network security. Moreover, the dynamics of the networks makes the manual identification of network segments nearly impossible. In this paper, we inspect the possibilities of the behavior-aware network segmentation using IP flows and machine learning approaches that would enable to identify segments automatically, even in a complex network. We evaluate the suitability of clustering algorithms for identification of behavior-consistent segments in a network. We show that the clustering algorithms can identify relevant behavior-consistent clusters that overlap with those identified manually by experts. Apart from the segment identification, we investigate the other essential task of network segmentation process: assignment of an unknown host to an existing segment. We evaluate the performance of four different classification mechanisms on a real-world dataset. We show that it is possible to assign an unknown host to an appropriate network segment with up to 92% precision. Moreover, we release the whole dataset and experiment steps available for public use.

© 2019 Association for Computing Machinery. Web applications are evolving to a decentralized, client-centric architecture in which browsers need to be able to put the user back in control of their personal data, need to be able to operate in disconnected settings, and need to offload the web server as much as possible. This paper presents a set of key application scenarios and trends in different business domains that require a more client-centric and data-centric web middleware for decentralized, peer-to-peer web applications in the edge. We define a set of key requirements for data operations in such middleware and motivate them with the application cases. This paper further discusses the current state and limitations of the browser as a platform for peer-to-peer communication and complex decentralized applications with shared data. We conclude with a performance assessment of our first prototype middleware for client-centric and data-centric peer-to-peer web applications. ispartof: pages:7-11 ispartof: Proceedings of the 2nd International Workshop on Edge Systems, Analytics and Networking pages:7-11 ispartof: EdgeSys '19 location:Dresden, Germany date:25 Mar 2019 status: Published online

The Internet of Things (IoT) enables connected devices that are an integral part of the physical world. The possibility to connect, manage, configure and dynamically reprogram remote devices through local and global cloud environments will open up a broad variety of new use cases, services, applications and device categories, and will enable entirely new product and application ecosystems as well. In this paper we discuss the software architecture options of IoT gateways as a follow-up to our earlier paper that defined a taxonomy of software architectures for IoT devices. We summarize several different software architecture options for IoT gateways. These options have a significant impact on the overall end-to-end architecture and topology of IoT systems, e.g., in determining how much computation can be performed on the edge of the network. Based on our observations and industry experiences we then make predictions on the future of gateway solutions and IoT systems more broadly. © 2019 ACM.

Personalized content provided by recommender systems is an integral part of the current online news reading experience. However, news recommender systems are criticized for their 'black-box' approach to data collection and processing, and for their lack of explainability and transparency. This paper focuses on explaining user profiles constructed from aggregated reading behavior data, used to provide content-based recommendations. The paper makes a first step toward consolidating epistemic values of news providers and news readers. We present an evaluation of an explanation interface reflecting these values, and find that providing users with different goals for self-actualization (i.e., Broaden Horizons vs. Discover the Unexplored) influences their reading intentions for news recommendations.

Involving users is crucial to designing technology successfully, especially for vulnerable users in health and social care, yet detailed descriptions and critical reflections on the co-design process, techniques and methods are rare. This paper introduces the PERCEPT (PERrsona-CEntred Participatory Technology) approach for the co-design process and we analyse and discuss the lessons learned for each step in this process. We applied PERCEPT in a project to develop a smart home toolset that will allow a person living with early stage dementia or Parkinson's to plan, monitor and self-manage his or her life and well-being more effectively. We present a set of personas which were co-created with people and applied throughout the project in the co-design process. The approach presented in this paper will enable researchers and designers to better engage with target user groups in co-design and point to considerations to be made at each step for vulnerable users.

Dependent types are a powerful tool for maintaining program invariants. To take advantage of this aspect in real-world programming, efforts have been put into enriching dependently typed languages with missing constructs, most notably, effects. This paper presents a language that has two practically interesting ingredients: dependent inductive types, and the delimited control constructs shift and reset. When integrating delimited control into a dependently typed language, however, two challenges arise. First, the dynamic nature of control operators, which is the source of their expressiveness, can break fundamental language properties such as logical consistency and subject reduction. Second, CPS translations, which we often use to define the semantics of control operators, do not scale straightforwardly to dependently typed languages. We solve the former issue by restricting dependency of types, and the latter using answer-type polymorphism of pure terms. The main contribution of this paper is to give a sound type system of our language, as well as a type-preserving CPS translation. We also discuss various extensions, which would make our language more like a full-spectrum proof assistant but pose non-trivial issues.

This paper presents some findings on an empirical study conducted to understand the effects of adopting agile methodologies in indus- trial software projects in the Apulian district (south of Italy). From 2014 to 2016, eleven software houses of the district migrated from traditional to agile methodologies, and collected an interesting set of measures during the transition. This paper reports some findings on collected data. Even if the limited set of subjects does not allow for a sound, robust statistical analysis, some preliminary results are interesting and show possible trends that may motivate further research and empirical assessments.

The current process of transformation affecting the energy system is calling for completely new approaches. This paper investigates the possibility of introducing energy packets as a fundamentally new abstraction concept that is following the transformation of communication networks in the 1970s from synchronous circuit switching to asynchronous store-and-forward routing. Focus is placed on the exploitation of power electronic devices in creating information embedded into the power flow. Considerations on some criticalities and future developments that are needed to further proceed on the development of this new vision are discussed. A simple test in Matlab/SIMULINK is provided in support for the packet dispatching described in the paper.

When publishing data, data licences are used to specify the actions that are permitted or prohibited, and the duties that target data consumers must comply with. However, in complex environments such as a smart city data portal, multiple data sources are constantly being combined, processed and redistributed. In such a scenario, deciding which policies apply to the output of a process based on the licences attached to its input data is a difficult, knowledgeintensive task. In this paper, we evaluate how automatic reasoning upon semantic representations of policies and of data flows could support decision making on policy propagation. We report on the results of a user study designed to assess both the accuracy and the utility of such a policy-propagation tool, in comparison to a manual approach. The authors would like to thank Francesco Osborne and Paul Mulholland for the constructive feedback on a previous version of this paper. non-peer-reviewed

Developers often require different concurrency models to fit the various concurrency needs of the different parts of their applications. Many programming languages, such as Clojure, Scala, and Haskell, cater to this need by incorporating different concurrency models. It has been shown that, in practice, developers often combine these concurrency models. However, they are often combined in an ad hoc way and the semantics of the combination is not always well-defined. The starting hypothesis of this paper is that different concurrency models need to be carefully integrated such that the properties of each individual model are still maintained. This paper proposes one such combination, namely the combination of the actor model and software transactional memory. In this paper we show that, while both individual models offer strong safety guarantees, these guarantees are no longer valid when they are combined. The main contribution of this paper is a novel hybrid concurrency model called transactional actors that combines both models while preserving their guarantees. This paper also presents an implementation in Clojure and an experimental evaluation of the performance of the transactional actor model.

In his famous paper entitled "Tackling the Awkward Squad", Peyton Jones studies how features that traditionally did not fit in the functional programming paradigm can be added to a functional language via careful language design (e.g. using monads), instead of allowing programmers to sprinkle around impure expressions and ad-hoc library calls, thereby turning the entire program into a non-functional program. Similarly, in this paper, we identify a number of code characteristics that do not map onto the reactive programming paradigm but that are present in many real life reactive programs. We propose a novel Actor-Reactor model that can serve as the basis for future language designs that allow a programmer to use the awkward squad without making the reactive parts of the program accidentally non-reactive.

Design of text entry on small screen devices, e.g. smartwatches, faces two related challenges: trading off a reasonably sized keyboard area against space to display the entered text and the concern over "fat fingers". This paper investigates tap accuracy and revisits layered interfaces to explore a novel layered text entry method. A two part user study identifies preferred typing and reading tilt angles and then investigates variants of a tilting layered keyboard against a standard layout. We show good typing speed (29 wpm) and very high accuracy on the standard layout - contradicting fears of fat-fingers limiting watch text-entry. User feedback is positive towards tilting interaction and we identify ∼14° tilt as a comfortable typing angle. However, layering resulted in slightly slower and more erroneous entry. The paper contributes new data on tilt angles and key offsets for smartwatch text entry and supporting evidence for the suitability of QWERTY on smartwatches.

This paper explores the combination of multiple concurrent modalities for conveying emotional information in HCI: temperature, vibration and abstract visual displays. Each modality has been studied individually, but can only convey a limited range of emotions within two-dimensional valence-arousal space. This paper is the first to systematically combine multiple modalities to expand the available affective range. Three studies were conducted: Study 1 measured the emotionality of vibrotactile feedback by itself; Study 2 measured the perceived emotional content of three bimodal combinations: vibrotactile + thermal, vibrotactile + visual and visual + thermal. Study 3 then combined all three modalities. Results show that combining modalities increases the available range of emotional states, particularly in the problematic top-right and bottom-left quadrants of the dimensional model. We also provide a novel lookup resource for designers to identify stimuli to convey a range of emotions.

This paper reports an evaluation of digital support for human creativity to improve health-and-safety in one manufacturing plant. It reports the use of this support as part of the plant's risk management process over 66 working days. Results revealed that this use led to more complete, more useful and more novel risk resolutions, compared with the original paper process, and informed how digital creativity support can be rolled out across manufacturing plants, as well as to other domains not recognized as creative.

peer-reviewed Recent CSCW research has shown that nomadicity can be seen as a dynamic process that emerges as people engage with practices supporting them in the mobilisation of their workplace to accomplish work in and across different locations. This paper elaborates on the emergent aspects of the process by detailing a spectrum of motivational and contextual forces that surround and shape nomadic practices. The paper contributes to existing CSCW literature on nomadicity and extends it by articulating the complex intersections of motive and context that shape nomadic practices. The findings that the paper presents emerged from an ethnographic study of a group of academics and their nomadic work/life practices. peer-reviewed

This paper describes our submission to Task 5 of SemEval 2017, Fine-Grained Sentiment Analysis on Financial Microblogs and News, where we limit ourselves to performing sentiment analysis on news headlines only (track 2). The approach presented in this paper uses a Support Vector Machine to do the required regression, and besides unigrams and a sentiment tool, we use various ontology-based features. To this end we created a domain ontology that models various concepts from the financial domain. This allows us to model the sentiment of actions depending on which entity they are affecting (e.g., ‘decreasing debt’ is positive, but ‘decreasing profit’ is negative). The presented approach yielded a cosine distance of 0.6810 on the official test data, resulting in the 12th position.

In this paper we present a low-intrusive approach to the detection of expressive full-body movement qualities. We focus on two qualities: Lightness and Fragility and we detect them using the data captured by four wearable devices, two Inertial Movement Units (IMU) and two electromyographs (EMG), placed on the forearms. The work we present in the paper stems from a strict collaboration with expressive movement experts (e.g., contemporary dance choreographers) for defining a vocabulary of basic movement qualities. We recorded 13 dancers performing movements expressing the qualities under investigation. The recordings were next segmented and the perceived level of each quality for each segment was ranked by 5 experts using a 5-points Likert scale. We obtained a dataset of 150 segments of movement expressing Fragility and/or Lightness. In the second part of the paper, we define a set of features on IMU and EMG data and we extract them on the recorded corpus. We finally applied a set of supervised machine learning techniques to classify the segments. The best results for the whole dataset were obtained with a Naive Bayes classifier for Lightness (F-score 0.77), and with a Support Vector Machine classifier for Fragility (F-score 0.77). Our approach can be used in ecological contexts e.g., during artistic performances.

GPS has become the reference for outdoor positioning, implementing a direct connection between the GPS satellite and a receiver device. Indoor positioning raises new challenges, locating a target device requires the wireless sensors networks and other technologies. Sensor networks deployed in buildings are commonly used for many applications based on location: surveillance, detection, navigation, etc. These indoor locating sensors generate lot of data related to tracking information. Exploiting this information for investigation issues for example remains a relevant purpose. The context of this paper is related to indoor locations systems based on wireless cell, ICCARD sensors and video surveillance cameras. In this context, as no global reference system similar to GPS is available, the location information issued from various systems, platforms, devices, etc. have neither standards nor common formats, and remain heterogeneous. This heterogeneity is mainly due to the different types of positions (geometric, symbolic, etc.) expressed w.r.t. various reference systems. In order to manage them in a given framework, it is necessary to homogenize the relevant (Meta) data to process the global knowledge they can give. This paper presents a contribution to extend our framework [1] to information generated by location sensor networks deployed in an indoor environment. The use case is illustrated in a forensic application [2].

© 2016 ACM. Shape changing interfaces give physical shapes to digital data so that users can feel and manipulate data with their hands and bodies. However, physical objects in our daily life not only have shape but also various material properties. In this paper, we propose an interaction technique to represent material properties using shape changing interfaces. Specifically, by integrating the multi-modal sensation techniques of haptics, our approach builds a perceptive model for the properties of deformable materials in response to direct manipulation. As a proof-of-concept prototype, we developed preliminary physics algorithms running on pin-based shape displays. The system can create computationally variable properties of deformable materials that are visually and physically perceivable. In our experiments, users identify three deformable material properties (flexibility, elasticity and viscosity) through direct touch interaction with the shape display and its dynamic movements. In this paper, we describe interaction techniques, our implementation, future applications and evaluation on how users differentiate between specific properties of our system. Our research shows that shape changing interfaces can go beyond simply displaying shape allowing for rich embodied interaction and perceptions of rendered materials with the hands and body.

© 2016 Copyright held by the owner/author(s). Cloud computing provides an innovative delivery model that enables enterprises to reduce operational costs and improve flexibility and scalability. Organisations wishing to migrate their legacy systems to the cloud often need to go through a difficult and complicated decision-making process. This can be due to multiple factors including restructuring IT resources, the still evolving nature of the cloud environment, and the continuous expansion of the services offered. These have increased the requirement for tools and techniques to help the decision-making process for migration. Although significant contributions have been made in this area, there are still many aspects which require further support. This paper evaluates the existing level of support to aid the decision-making process. It examines the complexity of decisions, evaluates the current state of Decision Support Systems in respect of migrating to the cloud, and analyses three models that proposed support for the migration processes. This paper identifies the need for a coherent approach for supporting the whole decision-making process. Further, it explores possible new approaches for addressing the complex issues involved in decision-making for migrating to the cloud.

This paper proposed a spherical camera ball and its image processing algorithm, designed to provide a ball's point of view (POV) for spectating of ball sports. The proposed spherical camera ball has six cameras embedded at fixed intervals around the surface of the ball. One of the main issues for such ball-type cameras is that the device is spinning and therefore it is hard to obtain stable video stream from such spinning cameras. This paper proposed automatic selection of cameras using matching scores between the anchor frame and current frame. The resultant movie will then always shows the point of interest within the frame. We then applied image translation to obtain a pseudo straight view in which the point of interest is always shown in the center of the frame.

Recently, several solutions have been proposed for realizing microfluidic switches able to route incoming microfluidic packets towards the intended output interface. In existing solutions, however, microfluidic frames consist of two droplets only: one contains the payload, whereas the other is used for signaling purposes only. As a consequence efficiency of such solution is very small.In this paper the above limitation is overcome by proposing microfluidic switches that can route microfluidic frames consisting of several, i.e, more than two, droplet. In such packets one droplet is used for signaling purposes only, whereas all the others carry payload. Therefore, efficiency increases.In this paper the proposed solution is described, analyzed and assessed through simulations.

The Actor Model is a message passing concurrency model that was originally proposed by Hewitt et al. in 1973. It is now 43 years later and since then researchers have explored a plethora of variations on this model. This paper presents a history of the Actor Model throughout those years. The goal of this paper is not to provide an exhaustive overview of every actor system in existence but rather to give an overview of some of the exemplar languages and libraries that influenced the design and rationale of other actor systems throughout those years. This paper therefore shows that most actor systems can be roughly classified into four families, namely: Classic Actors, Active Objects, Processes and Communicating Event-Loops. This paper also defines the Isolated Turn Principle as a unifying principle across those four families. Additionally this paper lists some of the key properties along which actor systems can be evaluated and formulates some general insights about the design and rationale of the different actor families across those dimensions.

This paper presents the support for interaction protocols that has been recently added to the JADEL programming language. JADEL is an agent-oriented programming language designed to ease the development of JADE agents and multi-agent systems by offering general-purpose agent-oriented abstractions to the programmer. The first part of the paper presents JADEL and motivates the need for a new agent-oriented programming language. Then, the agent-oriented abstractions that JADEL has been providing since its first version-namely agents, behaviours and communication ontologies-are described. The new support for interaction protocols is finally presented, and a simple example of a JADEL multi-agent system that uses interaction protocols is reported. The paper is concluded with an overview of the current state of JADEL and related tools.

In this paper we propose an algorithm for counting moving objects in outdoor environments. Similar to other approaches the proposed algorithm uses a traditional surveillance system approach: background subtraction followed by noise removing, tracking and object labeling. The novelty of the proposed algorithm is that each processing step uses a stereo camera. In fact, the algorithms use both rectified and depth images obtained with a stereo camera. Moving objects are extracted from the scene using a novel background subtraction approach. In outdoor environment the images can be degraded by noise. We considered two types of noise, namely periodic movements due to the wind and the cast shadow. In this paper novel algorithms for detecting these types of noise are proposed. Using them, the noisy pixels are removed. The resulting segmented pixels are grouped together by clustering connected regions and then tracked during their movements. The obtained blobs, which correspond to the moving objects, are thus obtained with high accuracy. The final part of the algorithm is blob classification, which identifies the moving objects. The knowledge of the moving objects can be used to build more complex counting applications than that based on just counting blobs. Two simple applications based on the proposed algorithm are worked out and discussed in this paper, namely one that counts the people moving on the left and on the right of the video scene and one that counts the cars moving in the same way.

In addition to conventional web browsers, WebView is used to display web content on Android. WebView is a component that enables the display of web content in mobile applications, and is extensively used. As WebView displays web content without having to redirect the user to web browsers, there is the possibility that unauthorized web access may be performed secretly via Web-View, and information in Android may be stolen or tampered with. Therefore, it is necessary to monitor and analyze web access via WebView, particularly because attacks exploiting WebView have been reported. However, there is no mechanism for monitoring web access viaWebView. In this work, the goals are to monitor web access via WebView and to analyze mobile applications using Web-View. To achieve these goals, we propose a web access monitoring mechanism for Android WebView. In this paper, the design and implementation of a mechanism that does not require any modifications to the Android Framework and Linux kernel are presented for the Chromium Android System WebView app. In addition, this paper presents evaluation results for the proposed mechanism.

This paper explores the suitability of structured (and declarative) multimedia document formats for supporting a novel type of performing arts: distributed theatre. In distributed theatre, the actors are split between two (or more) locations, but together deliver a single performance mediated by the cameras, the internet, and projection technologies. Based on our efforts to make an actual distributed theatre production happen (the Tempest by Miracle Theatre), this paper reflects on our experience. Our findings are divided into two main areas: workflow and document structure. We conclude that novel types of video-mediated applications, like distributed theatre, require new manners of authoring documents. Moreover, specific extensions to existing document formats are needed in order to accommodate the new requirements imposed by such kind of applications.

In this paper we focus on three aspects of multimodal expressions of laughter. First, we propose a procedural method to synthesize rhythmic body movements of laughter based on spectral analysis of laughter episodes. For this purpose, we analyze laughter body motions from motion capture data and we reconstruct them with appropriate harmonics. Then we reduce the parameter space to two dimensions. These are the inputs of the actual model to generate a continuum of laughs rhythmic body movements. In the paper, we also propose a method to integrate rhythmic body movements generated by our model with other synthetized expressive cues of laughter such as facial expressions and additional body movements. Finally, we present a real-time human-virtual character interaction scenario where virtual character applies our model to answer to human's laugh in real-time. \

Accuracy, completeness, and performance are all major concerns in the context of dynamic program analysis. Emphasizing one of these factors may compromise the other factors. For example, improving completeness of an analysis may seriously impair performance. In this paper, we present an analysis model and a framework that enables reducing analysis overhead at runtime through adaptive instrumentation of the base program. Our approach targets analyses implemented with code instrumentation techniques on the Java platform. Overhead reduction is achieved by removing instrumentation from code locations that are considered unimportant for the analysis results, thereby avoiding execution of analysis code for those locations. For some analyses, our approach preserves result accuracy and completeness. For other analyses, accuracy and completeness may be traded for a major performance improvement. In this paper, we explore accuracy, completeness, and performance of our approach with two concrete analyses as case studies.