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- Hypermedia APIs for the Web of ThingsPublication . Martins, Jaime; Mazayev, Andriy; Correia, NoéliaThe Web of Things is a new and emerging concept that defines how the Internet of Things can be connected using common Web technologies, by standardizing device interactions on upper-layer protocols. Even for devices that can only communicate using proprietary vendor technologies, upper-layer protocols can generally provide the necessary contact points for a high degree of interoperability. One of the major development issues for this new concept is creating efficient hypermedia-enriched application programming interfaces (APIs) that can map physical Things into virtual ones, exposing their properties and functionality to others. This paper does an in-depth comparison of the following six hypermedia APIs: 1) the JSON Hypertext Application Language from IETF; 2) the Media Types for Hypertext Sensor Markup from IETF; 3) the Constrained RESTful Application Language from IETF'; 4) the Web Thing Model from Evrythng; 5) the Web of Things Specification from W3C; and 6) the Web Thing API from Mozilla.
- Luminance, colour, viewpoint and border enhanced disparity energy modelPublication . Martins, Jaime; Rodrigues, Joao; du Buf, J. M. H.The visual cortex is able to extract disparity information through the use of binocular cells. This process is reflected by the Disparity Energy Model, which describes the role and functioning of simple and complex binocular neuron populations, and how they are able to extract disparity. This model uses explicit cell parameters to mathematically determine preferred cell disparities, like spatial frequencies, orientations, binocular phases and receptive field positions. However, the brain cannot access such explicit cell parameters; it must rely on cell responses. In this article, we implemented a trained binocular neuronal population, which encodes disparity information implicitly. This allows the population to learn how to decode disparities, in a similar way to how our visual system could have developed this ability during evolution. At the same time, responses of monocular simple and complex cells can also encode line and edge information, which is useful for refining disparities at object borders. The brain should then be able, starting from a low-level disparity draft, to integrate all information, including colour and viewpoint perspective, in order to propagate better estimates to higher cortical areas.
- An integrated framework for combining gist vision with object segregation categorisation and recognitionPublication . Rodrigues, J. M. F.; Almeida, D.; Martins, Jaime; Lam, RobertoThere are roughly two processing systems: (1) very fast gist vision of entire scenes, completely bottom-up and data driven, and (2) Focus-of-Attention (FoA) with sequential screening of specific image regions and objects. The latter system has to be sequential because unnormalised input objects must be matched against normalised templates of canonical object views stored in memory, which involves dynamic routing of features in the visual pathways.
- Cortical multiscale line-edge disparity modelPublication . Rodrigues, J. M. F.; Martins, Jaime; Lam, Roberto; du Buf, J. M. H.Most biological approaches to disparity extraction rely on the disparity energy model (DEM). In this paper we present an alternative approach which can complement the DEM model. This approach is based on the multiscale coding of lines and edges, because surface structures are composed of lines and edges and contours of objects often cause edges against their background. We show that the line/edge approach can be used to create a 3D wireframe representation of a scene and the objects therein. It can also significantly improve the accuracy of the DEM model, such that our biological models can compete with some state-of-the-art algorithms from computer vision.
- Interoperability in IoT through the semantic profiling of objectsPublication . Mazayev, Andriy; Martins, Jaime; Correia, NoéliaThe emergence of smarter and broader people-oriented IoT applications and services requires interoperability at both data and knowledge levels. However, although some semantic IoT architectures have been proposed, achieving a high degree of interoperability requires dealing with a sea of non-integrated data, scattered across vertical silos. Also, these architectures do not fit into the machine-to-machine requirements, as data annotation has no knowledge on object interactions behind arriving data. This paper presents a vision of how to overcome these issues. More specifically, the semantic profiling of objects, through CoRE related standards, is envisaged as the key for data integration, allowing more powerful data annotation, validation, and reasoning. These are the key blocks for the development of intelligent applications.
- Low-cost natural interface based on head movementsPublication . Martins, Joao M. S.; Rodrigues, Joao; Martins, Jaime; Velasco, C; Weber, G; Barroso, J; Mohamad, Y; Paredes, HSometimes people look for freedom in the virtual world. However, not all have the possibility to interact with a computer in the same way. Nowadays, almost every job requires interaction with computerized systems, so people with physical impairments do not have the same freedom to control a mouse, a keyboard or a touchscreen. In the last years, some of the government programs to help people with reduced mobility suffered a lot with the global economic crisis and some of those programs were even cut down to reduce costs. This paper focuses on the development of a touchless human-computer interface, which allows anyone to control a computer without using a keyboard, mouse or touchscreen. By reusing Microsoft Kinect sensors from old videogames consoles, a cost-reduced, easy to use, and open-source interface was developed, allowing control of a computer using only the head, eyes or mouth movements, with the possibility of complementary sound commands. There are already available similar commercial solutions, but they are so expensive that their price tends to be a real obstacle in their purchase; on the other hand, free solutions usually do not offer the freedom that people with reduced mobility need. The present solution tries to address these drawbacks. (C) 2015 Published by Elsevier B.V.
- Semantic web thing architecturePublication . Mazayev, Andriy; Martins, Jaime; Correia, NoéliaAs the Internet of Things evolves and matures, the number of connected devices and the amount of generated data grows exponentially. Integrative standards and API design patterns are required to deal with this fast growth, while easing machine to machine communication and promoting ubiquitous computing. This paper discusses the W3C Web of Things model that is currently in the process of standardization, and presents our overview and implementation of this model.
- A comprehensive approach for optimizing controller placement in Software-Defined NetworksPublication . Schutz, G.; Martins, JaimeSoftware-Defined Networks (SDNs) are characterized by dividing a network architecture in a data plane (i.e., any packet-relaying nodes like switches or routers) and a control plane, where specialized controllers assign forwarding decisions to the underlying data plane, and must do so in a very short timeframe. Thus, controllers play a key role in SDNs and the Controller Placement Problem (CPP) becomes a critical issue, affecting network delays and synchronization. If there are significant propagation delays between controllers and nodes, or among controllers, their ability to quickly react to network events is affected, degrading reliability. In this work, we propose a comprehensive mathematical formalization of the CPP, which constrains propagation latency and controller capacity, and determines simultaneously the minimum number of controllers, their location and the assignment of nodes to each, while keeping a balanced load distribution among controllers. As CPP is NP-hard, a heuristic approach is also presented. Simulations for 60 network scenarios show that this approach obtains balanced and resilient solutions, in negligible time, which are proven to be optimal or near optimal for 90% of the evaluated cases.
- Region segregation and saliency using colour informationPublication . Martins, Jaime; Rodrigues, J. M. F.; du Buf, J. M. H.Saliency maps determine the likelihood that we focus on interesting areas of scenes or images. These maps can be built using several low-level image features, one of which having a particular relevance: colour. In this paper we present a new computational model, based only on colour features, which provides a sound basis for saliency maps for static images and video, plus region segregation and cues for local gist vision.
- Biological models for active vision: towards a unified architecturePublication . Terzic, Kasim; Lobato, D.; Saleiro, Mário; Martins, Jaime; Farrajota, Miguel; Rodrigues, J. M. F.; du Buf, J. M. H.Building a general-purpose, real-time active vision system completely based on biological models is a great challenge. We apply a number of biologically plausible algorithms which address different aspects of vision, such as edge and keypoint detection, feature extraction,optical flow and disparity, shape detection, object recognition and scene modelling into a complete system. We present some of the experiments from our ongoing work, where our system leverages a combination of algorithms to solve complex tasks.