Scalability is recognised as a primary factor to be considered in the design of distributedsystems. The scalability of object-oriented middleware CORBA is becoming a major concern as it has emerged as a standard arch...
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Scalability is recognised as a primary factor to be considered in the design of distributedsystems. The scalability of object-oriented middleware CORBA is becoming a major concern as it has emerged as a standard architecture for distributed object computing. In this paper, a systematic scalability analysis of the basic components of the CORBA specification is attempted. From this analysis, the Portable Object Adapter (POA) and the Implementation Repository (IR) are identified to influence the scale of a CORBA-based system. The specification of the POA provides enough feasibility for the application designer to handle scalability. The existing implementations of IR have a tradeoff between scalability and object migration. A scalable design of the IR is proposed which allows individual objects to migrate without compromising scalability. A performance comparison of the proposed model with existing IR designs is made using a simulation study.
Data distribution management (DDM) is one of the services defined by the DoD High Level Architecture. DDM is necessary to provide efficient, scalable mechanisms for distributing state updates and interaction informati...
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Data distribution management (DDM) is one of the services defined by the DoD High Level Architecture. DDM is necessary to provide efficient, scalable mechanisms for distributing state updates and interaction information in large scale distributed simulations. We describe data distribution management mechanisms (also known as filtering) used for real time training simulations. We propose a new DDM approach to multicast group allocation, which we refer to as a dynamic grid-based allocation. Our scheme is based on a combination of a fixed grid-based method, known for its low overhead and ease of implementation, and a sender-based strategy, which uses fewer multicast groups than the fixed grid-based method. We describe our DDM algorithm, its implementation, and report on the performance results that we have obtained using the RTI-Kit framework. These results include the outcome of experiments comparing our approach to the fixed grid-based method, and they show that our scheme is scalable and significantly reduces the message overhead of previous grid-based allocation schemes.
Patterns are a means for capturing experience in solving general problems. They give general solutions to common and recurring problems. They exist at various phases of the software development life-cycle (SDLC), name...
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Patterns are a means for capturing experience in solving general problems. They give general solutions to common and recurring problems. They exist at various phases of the software development life-cycle (SDLC), namely the analysis phase, the design phase, the coding phase and the testing phase. Patterns in each phase are identified independently. It is possible for the patterns of one phase to be related to patterns in other phases. This paper proposes pattern mapping to inter-relate the patterns of various phases in SDLC to address this issue. It is advantageous to capture the related patterns of different phases as a single unit for software development. Reusable integrated components (ICs) of patterns are proposed to capture the related patterns. A software IC is a group of inter-related patterns, that gives solutions for a recurring problem at various phases of SDLC. A representation mechanism for ICs is presented using the URA (Unified Representation of an Artifact) model, which captures the software development process. Also, this paper proposes a software development process that is based on reusable ICs of patterns. The representation of a software project developed using ICs is also discussed.
In this paper we present an active video module that consists of a miniature video sensor, a wireless video transmitter and a pan-tilt mechanism driven by micromotors. The video module is part of a miniature mobile ro...
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In this paper we present an active video module that consists of a miniature video sensor, a wireless video transmitter and a pan-tilt mechanism driven by micromotors. The video module is part of a miniature mobile robot that is projected to areas of the environment to be surveyed. A single-chip CMOS video sensor and miniature brushless DC gearmotors are used to comply with restrictions imposed by the robotic system in terms of payload weight volume and power consumption. Different types of actuation are analyzed for compatibility with a mesoscale robotic system. Applications of an active video module are discussed.
We present a simulation testbed for wireless and mobile telecommunicationsystems, a two-stage PCS parallel simulation testbed which makes use of a conservative scheme at stage 1, and of time warp at stage 2. While ti...
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We present a simulation testbed for wireless and mobile telecommunicationsystems, a two-stage PCS parallel simulation testbed which makes use of a conservative scheme at stage 1, and of time warp at stage 2. While time warp is considered to be an effective synchronization mechanism in parallel and distributed discrete event simulation (PDES) it is also well known for its instability due to rollbacks and its devastating effect, i.e., series of cascading rollbacks, among other factors. Thus, our primary goal is to study the impact and the importance of partitioning in our PCS model while reducing significantly the number of rollbacks.
In some scenarios involving online transaction processing within a distributed database, it is desirable to synchronize transactions in a manner that guarantees conflict equivalence with a serial schedule ordered by o...
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In some scenarios involving online transaction processing within a distributed database, it is desirable to synchronize transactions in a manner that guarantees conflict equivalence with a serial schedule ordered by original transaction start times while providing each transaction with an anomaly-serializable isolation. Few theoretical concurrency control algorithms guarantee such a conflict equivalence, and we are unaware of any protocol that accomplishes this while supporting real-world issues such as out-of-order transaction messages, out-of-order operation executions and out-of-order transaction committals without the burden of explicit read-set and write-set declarations. We describe an algorithm called T3C (Temporally Correct Concurrency Control) that provides this guarantee and supports these issues while requiring only table-level write-set declarations.
If we are stepping out of windows (of the GUI kind), what are we stepping into? We suggest it is into cooperative buildings. For the foreseeable future, at least, we can identify two major characteristics of the coope...
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If we are stepping out of windows (of the GUI kind), what are we stepping into? We suggest it is into cooperative buildings. For the foreseeable future, at least, we can identify two major characteristics of the cooperative building. The spaces of the building will be augmented in various ways, providing an ambient environment that bridges spatial discontinuities in workgroups and provides a continuous window into the state of the virtual world. Secondly, the ways in which the spaces themselves are used will evolve to be more congruent with the fluid, dynamic and distributed nature of the work taking place in the building. These two characteristics are deeply interconnected. This evolution need not happen entirely in the physical world; the essence of a cooperative building will become the way in which it mixes both physical and virtual affordances to support the workaday activities of its inhabitants.
SCAF is a Simple Component Architecture Framework built upon OMG CORBA. Components are the core modelling concept. Components describe their relationship with other components by means of interface provision and requi...
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SCAF is a Simple Component Architecture Framework built upon OMG CORBA. Components are the core modelling concept. Components describe their relationship with other components by means of interface provision and requirement descriptions. These interfaces are the connectors that configure the distributed application. SCAF supports dynamic composition and encapsulation of components and has a simple matching specification for retrieval of reusable components. It has been implemented in Python on top, of an ORB (Object Request Broker) called Fnorb.
Today many applications routinely generate large quantities of data. The data often takes the form of (time) series, or more generally streams, i.e. an ordered sequence of records. Analysis of this data requires strea...
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Today many applications routinely generate large quantities of data. The data often takes the form of (time) series, or more generally streams, i.e. an ordered sequence of records. Analysis of this data requires stream processing techniques which differ in significant ways from what current database analysis and query techniques have been optimized for. In this paper we present a new operator, called StreamJoin, that can efficiently be used to solve stream-related problems of various applications, such as universal quantification, pattern recognition and data mining. Contrary to other approaches. StreamJoin processing provides rapid response times, a non-blocking execution as well as economical resource utilization. Adaptability to different application scenarios is realized by means of parameters. In addition, the StreamJoin operator can be efficiently embedded into the database engine, thus implicitly using the optimization and parallelization capabilities for the benefit of the application. The paper focuses on the applicability of StreamJoin to integrate application semantics into the DBMS.
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