Distributed Computation as Hierarchy

This paper presents a new distributed computational model of distributed systems called the phase web that extends V. Pratt's orthocurrence relation from 1986. The model uses mutual-exclusion to express sequence, and a new kind of hierarchy to replace event sequences, posets, and pomsets. The model explicitly connects computation to a discrete Clifford algebra that is in turn extended into homology and co-homology, wherein the recursive nature of objects and boundaries becomes apparent and itself subject to hierarchical recursion. Topsy, a programming environment embodying the phase web, is available from www.cs.auc.dk/topsy.Comment: 16 pages, 3 figure

Web System to Support the Teaching of an Undergraduate Distributed Systems Course

This paper introduces a web-based system that supports the teaching of an undergraduate (UG) distributed systems course. It specifically describes a web system that was developed to complement the functionality of web objects in the XML (WOX) framework. It allows for storing and visualizing the state of distributed objects, as well as displaying and executing methods through a web interface. Users can provide values for each of the parameters. The WOX framework is essential to note as it facilitates the development of distributed applications that are object-based and can interoperate among different object-oriented programming languages. WOX employs the XML format to represent objects and uses HTTP as the communication protocol

Orchestration of heterogeneous middleware services and its application to a comand and control platform

MSC Dissertation in Computer EngineeringDistributed objects was, until recently, the leading technology in the design and implementation of component-based architectures, such as the ones based on services, better known as Service-Oriented Architectures (SOA). Although established in the market for more than a decade, and therefore mature, these technologies have failed to overcome the porting of the SOA concept to the Web. Web services are a recent technology that has been growing in the last few years. Their acceptance has increased over enterprises and organizations as they seem to overcome the Web and interoperability related problems of the Distributed Objects technology. Web services provide interoperability between systems and that is undoubtedly a strength of this technology since this is a crucial aspect of nowadays business. Moreover, the widespread of services led to the recent introduction of the service composition concept, that although being a technology independent concept,is closely related to Web services and there is no tool support for other technologies. Nonetheless, distributed objects still play an important role in the development of distributed systems, namely due to performance issues that are important when it comes to the internals of a platform. However, the use of service composition in these distributed object-based platforms requires the exposure of their composing services as Web services. The main objective of this masters thesis is improve the state-of-the-art in the support for the composition of services originating from distributed objects-based platforms. Bearing in mind that these kind of platforms are composed by several services, the idea is to present a platform as a set of Web services in order to be able to orchestrate them

A Scalable Middleware Solution for Advanced Wide Area Web Services

To alleviate scalability problems in the Web, many researchers concentrate on how to incorporate advanced caching and replication techniques. Many solutions incorporate object-based techniques. In particular, Web resources are considered as distributed objects offering a well-defined interface. We argue that most proposals ignore two important aspects. First, there is little discussion on what kind of coherence should be provided. Proposing specific caching or replication solutions makes sense only if we know what coherence model they should implement. Second, most proposals treat all Web resources alike. Such a one-size-fits-all approach will never work in a wide-area system. We propose a solution in which Web resources are encapsulated in physically distributed shared objects. Each object should encapsulate not only state and operations, but also the policy by which its state is distributed, cached, replicated, migrated, etc

The Astronomer's Telegram: A Web-based Short-Notice Publication System for the Professional Astronomical Community

The Astronomer's Telegram (ATEL; http://fire.berkeley.edu:8080/) is a web based short-notice (<4000 characters) publication system for reporting and commenting on new astronomical observations, offering for the first time in astronomy effectively instantaneous distribution of time-critical information for the entire professional community. It is designed to take advantage of the World Wide Web's simple user interface and the ability of computer programs to provide nearly all the necessary functions. One may post a Telegram, which is instantly (<1 second) available at the Web-site, and distributed by email within 24 hours through the Daily Email Digest, which is tailored to the subject selections of each reader. Optionally, urgent Telegrams may be distributed through Instant Email Notices. While ATEL will be of particular use to observers of transient objects (such as gamma-ray bursts, microlenses, supernovae, novae, or X-ray transients) or in fields which are rapidly evolving observationally, there are no restrictions on subject matter.Comment: 4 pages, LaTeX, requires aaspp4.st

Improving Knowledge Retrieval in Digital Libraries Applying Intelligent Techniques

Nowadays an enormous quantity of heterogeneous and distributed information is stored in the digital University. Exploring online collections to find knowledge relevant to a user’s interests is a challenging work. The artificial intelligence and Semantic Web provide a common framework that allows knowledge to be shared and reused in an efficient way. In this work we propose a comprehensive approach for discovering E-learning objects in large digital collections based on analysis of recorded semantic metadata in those objects and the application of expert system technologies. We have used Case Based-Reasoning methodology to develop a prototype for supporting efficient retrieval knowledge from online repositories. We suggest a conceptual architecture for a semantic search engine. OntoUS is a collaborative effort that proposes a new form of interaction between users and digital libraries, where the latter are adapted to users and their surroundings