French Optical Telegraphy, 1793-1855: Hardware, Software, Administration

The relatively stable contribution of technological change to aggregate growth masks technological trajectories which are, at the sectoral level, often highly discontinuous. For decades, even centuries, the capabilities used to produce a particular good or service may continue essentially unchanged or with relatively minor evolutionary modifications. Sometimes without much warning a breakthrough innovation will create a new technological paradigm, along with an accompanying gale of creative destruction, which is then followed by a period of consolidation within a maturing framework

Distributed Concurrent Persistent Languages: An Experimental Design and Implementation

A universal persistent object store is a logical space of persistent objects whose localities span over machines reachable over networks. It provides a conceptual framework in which, on one hand, the distribution of data is transparent to application programmers and, on the other, store semantics of conventional languages is preserved. This means the manipulation of persistent objects on remote machines is both syntactically and semantically the same as in the case of local data. Consequently, many aspects of distributed programming in which computation tasks cooperate over different processors and different stores can be addressed within the confines of persistent programming. The work reported in this thesis is a logical generalization of the notion of persistence in the context of distribution. The concept of a universal persistent store is founded upon a universal addressing mechanism which augments existing addressing mechanisms. The universal addressing mechanism is realized based upon remote pointers which although containing more locality information than ordinary pointers, do not require architectural changes. Moreover, these remote pointers are transparent to the programmers. A language, Distributed PS-algol, is designed to experiment with this idea. The novel features of the language include: lightweight processes with a flavour of distribution, mutexes as the store-based synchronization primitive, and a remote procedure call mechanism as the message-based interprocess communication mechanism. Furthermore, the advantages of shared store programming and network architecture are obtained with the introduction of the programming concept of locality in an unobtrusive manner. A characteristic of the underlying addressing mechanism is that data are never copied to satisfy remote demands except where efficiency can be attained without compromising the semantics of data. A remote store operation model is described to effect remote updates. It is argued that such a choice is the most natural given that remote store operations resemble remote procedure calls

Third CLIPS Conference Proceedings, volume 2

Expert systems are computer programs which emulate human expertise in well defined problem domains. The C Language Integrated Production System (CLIPS) is an expert system building tool, developed at the Johnson Space Center, which provides a complete environment for the development and delivery of rule and/or object based expert systems. CLIPS was specifically designed to provide a low cost option for developing and deploying expert system applications across a wide range of hardware platforms. The development of CLIPS has helped to improve the ability to deliver expert system technology throughout the public and private sectors for a wide range of applications and diverse computing environments. The Third Conference on CLIPS provided a forum for CLIPS users to present and discuss papers relating to CLIPS applications, uses, and extensions

Multiscouting: Guiding distributed manipulation with multiple mobile sensors

This thesis investigates the use of multiple mobile sensors to guide the motion of a distributed manipulation system. In our system, multiple robots cooperatively place a large object at a goal in a dynamic, unstructured, unmapped environment. We take the system developed in [Rus, Kabir, Kotay, Soutter 1996], which employs a single mobile sensor for navigational tasks, and extend it to allow the use of multiple mobile sensors. This allows the system to perform successful manipulations in a larger class of spaces than was possible in the single scout model. We focus on the development of a negotiation protocol that enables multiple scouts to cooperatively plan system motion. This algorithm enhances the previous\u27 system\u27s scalability and adds greater fault-tolerance. Two alternate algorithms for cooperation: a modification of negotiation and a bidding protocol, are also discussed. Finally, an implementation of the negotiation protocol is described and experimental data produced by the implementation is analyzed

Implementation of an API for distributed communication between processes in closed contexts

Dissertação de mestrado integrado em Engenharia de ComunicaçõesExistem atualmente diversas Application Programming Interfaces (APIs) que ajudam na programação de aplicações distribuídas. Na maior parte dos casos, estas utilizam de forma in exível um único tipo de protocolo aplicacional e interface, cando dependente dos protocolos de transporte já existentes e do sistema operativo. Para o programador, a stack de protocolos e o tipo de interface têm que ser decididos explicitamente antes do estabelecimento da comunicação entre os processos. Algumas APIs facilitam a programação ocultando alguns aspetos espec í cos dos mecanismos e protocolos de comunicação utilizados, disponibilizando uma interface mais homogeneizada. No entanto, a programação continua a não ser totalmente transparente e independente dos protocolos de comunicação utilizados, dos sistemas operativos e da localização relativa dos processos comunicantes. Além disso, estas APIs não tomam decisões sobre o mecanismo de comunicação a utilizar quando existem várias alternativas possíveis, sendo esta decisão da responsabilidade do programador. Num contexto de implementação de simuladores distribuídos e modulares para protocolos de redes de computadores e sistemas de comunicação, seria vantajoso poder-se utilizar uma API para comunicação dos processos de simulação que disponibilizasse apenas um único interface de programação e que decidisse de forma transparente o mecanismo ou protocolo comunicacional mais e ciente, tendo em conta a localização relativa dos processos. Nesta dissertação são abordadas as soluções semelhantes já existentes e é estudada uma API que pretende preencher estas lacunas. A arquitetura desta API será depois apresentada, assim como uma solução com base na investigação realizada. Por m, os resultados dos testes serão analizados e a conclusão apresentada. Esta dissertação foi desenvolvida no contexto do projeto RoutUM, um simulador de redes de computadores atualmente a ser desenvolvido pela Universidade do Minho.There are several Application Programming Interfaces (APIs) available to simplify the development of distributed applications. In most cases, they invariably use one type of application protocol and interface, being dependent of the existing transport protocols and operating system. To the programmer, the protocol stack and the type of interface must be explicitly chosen before initiating communication between processes. Some APIs simplify programming by hiding some speci c aspects about the communication protocols and mechanisms, revealing a more homogenized interface. However, the programming is still not completely transparent and independent from the communication protocols, the operating system and the relative location of the communicating processes. Also, they are unable to decide which communication mechanism to be used when there are several available possibilities, leaving that responsibility to the programmer. On the context of implementation of distributed and modular simulators for network protocols and communication systems, it would be desirable to be able to use an API that would allow communication between the processes while providing only one programming interface. It would then transparently decide the most e cient mechanism or communication protocol from the relative location of the communicating processes. This dissertation will present and discuss the currently available solutions and the problems associated with the development of an API which attempts to ll the missing features indicated above. The API's architecture will then be shown and developed into a solution based on the results from the investigation. In the end, this solution will be tested and the nal results will be presented. This dissertation was developed in the context of the RoutUM project, a network simulator being currently developed in the University of Minho

Project Cerberus: Flyby Mission to Pluto

The goal of the Cerberus Project was to design a feasible and cost-effective unmanned flyby mission to Pluto. The requirements in the request for proposal for an unmanned probe to Pluto are presented and were met. The design stresses proven technology that will avoid show stoppers which could halt mission progress. Cerberus also utilizes the latest advances in the spacecraft industry to meet the stringent demands of the mission. The topics covered include: (1) mission management, planning, and costing; (2) structures; (3) power and propulsion; (4) attitude, articulation, and control; (5) command, control, and communication; and (6) scientific instrumentation

Effective interprocess communication (IPC) in a real-time transputer network

The thesis describes the design and implementation of an interprocess communication (IPC) mechanism within a real-time distributed operating system kernel (RT-DOS) which is designed for a transputer-based network. The requirements of real-time operating systems are examined and existing design and implementation strategies are described. Particular attention is paid to one of the object-oriented techniques although it is concluded that these techniques are not feasible for the chosen implementation platform. Studies of a number of existing operating systems are reported. The choices for various aspects of operating system design and their influence on the IPC mechanism to be used are elucidated. The actual design choices are related to the real-time requirements and the implementation that has been adopted is described. [Continues.