Mixed Programming Metaphors in a Shared Dataspace Model of Concurrency

The term shared dataspace refers to the general class of models and languages in which the principal means of communication is a common, content-addressable data structure called a dataspace. Swarm is a simple language we have used as a vehicle for the investigation of the shared dataspace approach to concurrent computation. It is the first shared dataspace language to have an associated assertional-style proof system. An important feature of Swarm is its ability to bring a variety of programming paradigms under a single, unified model. In a series of related examples we explore Swarm\u27s capacity to express shared-variable, message-passing, and rule-based computations; to specify synchronous and asynchronous processing models; and to accommodate highly dynamic program and data structures. Several illustrations make use of a programming construct unique to Swarm, the synchrony relation, and explain how this feature can be used to construct dynamically structured, partially synchronous computation. The paper has three parts: an overview the Swarm programming notation, an examination of Swarm programming strategies via a series of related example programs, and a discussion of the distinctive features of the shared dataspace model. A formal operational model for Swarm is presented in an appendix

Coordination Models for Internet of Things

In constrained environments, there is a variety of devices like sensors and actuators with limited computation power or energy that form an Internet of Things (IoT) system. When processing complex tasks is required, those devices send the data to the cloud and obtain the result later. However, the IoT system could process complex task if more devices work together, sharing computational resources and cooperating. This cooperation can be achieved using a coordination model that distributes the load among the different devices based on a set of parameters, laws and defined entities. This research implements and evaluates a data-oriented coordination model with three variations for Internet of Things (IoT). It also presents, implements and evaluates a new process-oriented coordination model that can make constrained environments much more effective and allow the processing of more complex tasks closer to the network. The development of all the coordination models was focused on using the system’s computational resources effectively. As IoT is a heterogeneous field, devices with more power can process more complex tasks, creating an uneven but adequate load distribution. Various experiments were conducted to evaluate the performance of each model using one and two workers. The results showed that every coordination model works effectively when distributing the load among more workers. For the process-oriented model, implementing some CoAP features allowed the system to perform better when repetitive tasks are required

Constraint-based protocols for distributed problem solving

AbstractDistributed Problem Solving (DPS) approaches decompose problems into subproblems to be solved by interacting, cooperative software agents. Thus, DPS is suitable for solving problems characterized by many interdependencies among subproblems in the context of parallel and distributed architectures. Concurrent Constraint Programming (CCP) provides a powerful execution framework for DPS where constraints define local problem solving and the exchange of information among agents declaratively. To optimize DPS, the protocol for constraint communication must be tuned to the specific kind of DPS problem and the characteristics of the underlying system architecture. In this paper, we provide a formal framework for modeling different problems and we show how the framework applies to simple yet generalizable examples

Coordination and P2P computing

Peer-to-Peer (P2P) refers to a class of systems and/or applications that use distributed resources in a decentralized and autonomous manner to achieve a goal. A number of successful applications, like BitTorrent (for file and content sharing) and SETI@Home (for distributed computing) have demonstrated the feasibility of this approach. As a new form of distributed computing, P2P computing has the same coordination problems as other forms of distributed computing. Coordination has been considered an important issue in distributed computing for a long time and many coordination models and languages have been developed. This research focuses on how to solve coordination problems in P2P computing. In particular, it is to provide a seamless P2P computing environment so that the migration of computation components is transparent. This research extends Manifold, an event-driven coordination model, to meet P2P computing requirements and integrates the P2P-Manifold model into an existing platform. The integration hides the complexity of the coordination model and makes the model easy to use

Development and Specification of Virtual Environments

This thesis concerns the issues involved in the development of virtual environments (VEs). VEs are more than virtual reality. We identify four main characteristics of them: graphical interaction, multimodality, interface agents, and multi-user. These characteristics are illustrated with an overview of different classes of VE-like applications, and a number of state-of-the-art VEs. To further define the topic of research, we propose a general framework for VE systems development, in which we identify five major classes of development tools: methodology, guidelines, design specification, analysis, and development environments. Of each, we give an overview of existing best practices

Defining digital space through a visual language

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Architecture, 2000.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Includes bibliographical references (p. 110-111).Current approaches toward digital spaces mainly mimic the physical space that surrounds us. While this approach is valid in a wide range of applications and research, the goal of this thesis is to propose an alternative approach towards digital space based on principles of vision and memory to provide a theoretical framework for the development of a model for accessing and monitoring information. The core idea is to incorporate the principle of dynamic reaction of the space model to the point of attention of the user through methodically scaling the level of detail. The intention behind the creation of such a model is to enhance the communication between the information and the user as well as to allow multiple users to collectively influence and expand the space they view. This involves the definition of a visual language, definition of the space model and multi-user relations. Techniques proposed in this thesis are gaze tracking to map the point of attention and the programming of visual interfaces that respond dynamically to user input.by Axel Kilian.S.M

The Design and Implementation of a Notional Machine for teaching Introductory Programming

Comprehension of both programming and programs is a difficult task for novices to master, with many university courses that feature a programming component demonstrating significant failure and drop out rates. Many theories exist that attempt to explain why this is the case. One such theory, originally postulated by du Boulay, is that students do not understand the properties of the machine; they do not understand what they are or how they are controlling them by writing code. This idea formed the development of the notional machine, which exists solely as an abstraction of the physical machine to aid with its understanding and comprehension. This work contributes a design for a new notional machine and a graphical notation for its representation. The notional machine is designed to work with object-oriented languages (in particular Java). It provides several novel contributions over pre-existing models -- while existing similar models are generally constrained to line by line operation, the notional machine presented here can scale effectively across many program sizes, from few objects and lines to many. In addition, it is able to be used in a variety of formats (in both electronic and unplugged form). It also melds together three traditionally separate diagrams that had to be understood simultaneously (the stack trace, class diagram and object heap.) Novis, an implemented version of the notional machine, is also presented and evaluated. It is able to create automatic and animated versions of notional machine diagrams, and has been integrated into BlueJ's main interface. Novis can present static notional machine diagrams at selected stages of program execution, or animate ongoing execution in real time. The evaluation of Novis is presented in two parts. It is first tested alongside a selection of methodically chosen textbook examples to ensure it can visualise a range of useful programs, and it then undergoes usability testing with a group of first year computer science students

Context Aware Service Oriented Computing in Mobile Ad Hoc Networks

These days we witness a major shift towards small, mobile devices, capable of wireless communication. Their communication capabilities enable them to form mobile ad hoc networks and share resources and capabilities. Service Oriented Computing (SOC) is a new emerging paradigm for distributed computing that has evolved from object-oriented and component-oriented computing to enable applications distributed within and across organizational boundaries. Services are autonomous computational elements that can be described, published, discovered, and orchestrated for the purpose of developing applications. The application of the SOC model to mobile devices provides a loosely coupled model for distributed processing in a resource-poor and highly dynamic environment. Cooperation in a mobile ad hoc environment depends on the fundamental capability of hosts to communicate with each other. Peer-to-peer interactions among hosts within communication range allow such interactions but limit the scope of interactions to a local region. Routing algorithms for mobile ad hoc networks extend the scope of interactions to cover all hosts transitively connected over multi-hop routes. Additional contextual information, e.g., knowledge about the movement of hosts in physical space, can help extend the boundaries of interactions beyond the limits of an island of connectivity. To help separate concerns specific to different layers, a coordination model between the routing layer and the SOC layer provides abstractions that mask the details characteristic to the network layer from the distributed computing semantics above. This thesis explores some of the opportunities and challenges raised by applying the SOC paradigm to mobile computing in ad hoc networks. It investigates the implications of disconnections on service advertising and discovery mechanisms. It addresses issues related to code migration in addition to physical host movement. It also investigates some of the security concerns in ad hoc networking service provision. It presents a novel routing algorithm for mobile ad hoc networks and a novel coordination model that addresses space and time explicitly

Vice : an interface designed for complex engineering software : an application of virtual reality

Concurrent Engineering has been taking place within the manufacturing industry for many years whereas the construction industry has until recently continued using the 'over the wall' approach where each task is completed before the next began. For real concurrent engineering in construction to take place there needs to be true collaborative working between client representatives, construction professionals, suppliers and subcontractors. The aim of this study was to design, develop and test a new style of user interface which promotes a more intuitive form of interaction than the standard desktop metaphor based interface. This new interface has been designed as an alternative for the default interface of the INTEGRA system and must also promote enhanced user collaboration. By choosing alternative metaphors that are more obvious to the user it is postulated that it should be possible for such an interface to be developed. Specific objectives were set that would allow the project aim to be fulfilled. These objectives are outlined below: To gain a better understanding of the requirements of successful concurrent engineering particularly at the conceptual design phase. To complete a thorough review of the current interfaces had to take place including any guidelines on how to create a "good user interface". To experience many of the collaboration systems available today so that an informed choice of application can be made. To learn the relevant skills required to design, produce and implement the interface of choice. To perform a user evaluation of the finished user interface to improve overall usability and further streamline the concurrent conceptual design. The user interface developed used a virtual reality environment to create a metaphor of an office building. Project members could then coexist and interact within the building promoting collaboration and at the same time have access to the remaining INTEGRA tools. The user evaluation proved that the Virtual Integrated Collaborative Environment (VICE) user interface was a successful addition to the INTEGRA system. The system was evaluated by a substantial number of different users which validates this finding. The user evaluation also provided positive results from two different demographics concluding that the system was easy, intuitive to use with the necessary functionality. Using metaphor based user interfaces is not a new concept. It has become standard practise for most software developers. There are arguments for and against these types of user interfaces. Some advanced users will argue that having such an interface limits their ability to make full use of the applications. However the majority of users do not come within this bracket and for them, metaphor based user interfaces are very useful. This is again evident from the user evaluation.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Supporting mobile mixed-reality experiences

Mobile mixed-reality experiences mix physical and digital spaces, enabling participants to simultaneously inhabit a shared environment online and on the streets. These experiences take the form of games, educational applications and new forms of performance and art, and engender new opportunities for interaction, collaboration and play. As mobile mixed-reality experiences move out of the laboratory and into more public settings they raise new challenges concerning how to support these experiences in the wild. This thesis argues that mobile mixed-reality experiences in which artists retain creative control over the content and operation of each experience, particularly those that are deployed as theatrical performances, require dedicated support for content authoring and reactive orchestration tools and paradigms in order to be successfully and robustly operated in public settings. These requirements are examined in detail, drawing on the experience of supporting four publicly toured mobile mixed-reality experiences; Can You See Me Now?, Uncle Roy All Around You, I Like Frank in Adelaide and Savannah, which have provided a platform to practically develop, refine and evaluate new solutions to answer these challenges in the face of presenting the experiences to many thousands of participants over a four year period. This thesis presents two significant supporting frameworks. The ColourMaps system enables designers to author location-based content by directly colouring over maps; providing a simple, familiar and yet highly flexible approach to matching location-triggers to complex physical spaces. It provides support for multiple and specialised content layers, and the ability to configure and manage other aspects of an experience, including filtering inaccurate position data and underpinning orchestration tools. Second, the Orchestration framework supports the day-to-day operation of public experiences; providing dedicated control-room tools for monitoring that reveal the content landscape and historical events, intervention and improvisation techniques for steering and shaping each participant's experience as it unfolds both physically and virtually, and processes to manage a constant flow of participants