Ihor Kuz

Component-based development helps to improve the modularity and reusability of embedded systems. Component models devised for embedded systems are typically restricted due to the limited computing, storage and power resources of the target systems. Most existing component models for embedded systems therefore only support a static component architecture and provide a simple and lightweight core. With the increasing demand for

ABSTRACT Model Driven Development (MDD) aims to raise the level of abstraction for software development by providing more powerful concepts for capturing and reusing knowledge in deployment platforms and languages. MDD approaches are gaining a foothold in industrial practice. This is being facilitated by the Object Management Group (OMG), which leads the standards development effort (MDA/MOF/UML) for MDD. Leading software tool vendors such as IBM and Microsoft, as well as many smaller vendors and open source projects, are developing technologies to support MDD. We therefore believe it is timely to explore the current leading research efforts in tools for MDD.

This paper is a complete revision of "A Framework for Consistent, Replicated Web Objects," published by the same authors in the Proceedings of the 18th International Conference on Distributed Computing Systems (ICDCS), May 1998, Amsterdam, pp. 276--284. An electronic version of the ICDCS paper can be found at http://www.cs.vu.nl/¸steen/globe/publications.html. Article summary. The current Web is running into serious scalability problems. The standard solution is to apply techniques like caching, replication, and distribution. Unfortunately, as the variety of Web applications continues to grow, it will be impossible to find a single solution that fits all needs. The authors advocate a different approach to tackling scaling problems. Instead of seeking a general-purpose solution, they argue that it makes more sense to look at each Web document separately. For each document, three issues need to be addressed: placement of replicas, required coherence, and best coherence proto...

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 WWW is experiencing explosive growth and an increasing number of security-sensitive applications make now use of it. To achieve worldwide scalability and reduce latency in handling user requests, many of these applications make extensive use of data replication through caches and Content Delivery Networks. However, such replication mechanisms place data on untrusted hosts, which introduces various security problems. In this paper we present an architecture that combines data content, replication strategies and security in one unified object model and offers integrity guarantees for Web documents replicated on non-secure servers.

Caching and replication techniques can improve latency of the Web, while reducing network traffic and balancing load among servers. However, no single strategy is optimal for replicating all documents. Depending on its access pattern, each document should use the policy that suits it best. This paper presents an architecture for adaptive replicated documents. Each adaptive document monitors its access pattern, and uses it to determine which strategy it should follow. When a change is detected in its access pattern, it re-evaluates its strategy to adapt to the new conditions. Adaptation comes at an acceptable cost considering to the benefits of per-document replication strategies. vrije Universiteit Faculty of Mathematics and Computer Science 1 Introduction Most Web users suffer from slow document transfers. The reasons for such high latencies include distance between the user and the document, and load of the intermediate network. One common solution is to maintain copies of ...

. To alleviate the scalability problems in the current Web, many researchers are concentrating on how to incorporate more advanced caching and replication techniques than those currently supported. 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. In other words, caching and replication is generally done independent of how and where a resource is used. 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. In our model, each object not only e...

This paper is a complete revision of "A Framework for Consistent, Replicated Web Objects," published by the same authors in the Proceedings of the 18th International Conference on Distributed Computing Systems (ICDCS), May 1998, Amsterdam, pp. 276--284. An electronic version of the ICDCS paper can be found at http://www.cs.vu.nl/¸steen/globe/publications.html. Article summary. The current Web is running into serious scalability problems. The standard solution is to apply techniques like caching, replication, and distribution. Unfortunately, as the variety of Web applications continues to grow, it will be impossible to find a single solution that fits all needs. The authors advocate a different approach to tackling scaling problems. Instead of seeking a general-purpose solution, they argue that it makes more sense to look at each Web document separately. For each document, three issues need to be addressed: placement of replicas, required coherence, and best coherence proto...

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.

Different ideas about object-orientationand distrib- uted computing have resulted in a large number of distributed-object models. Use of the same termi- nology with different meanings makes these models hard to compare. What is currently missing is a framework for describing object models which can be used to compare and classify them. An attempt at definingsuch a framework is presented in

In the world of P2P le-sharing things are moving fast. New networks based on new technologies keep appearing, while old ones are slow to disappear. Not only is there growth with regards to the number of networks and the underlying technologies used, but there is also growth in the application of these technologies. Whereas the original growth around P2P networks

ABSTRACT This paper describes ongoing work on a new technique for reducing the cost of assurance of large software systems by building on a verified component platform. From a component architecture description, we automatically derive a formal model of the system and a semantics for the runtime behaviour of generated inter-component communication code. We can prove wellformedness properties of the architecture automatically and provide a framework in which users can reason about their component code and its behaviour. By leveraging the isolation properties and communication guarantees of a formally verified platform, correctness arguments for critical components will be able to be derived independently and composed together to reason about system-level correctness.

Current operating systems lack well-defined protocols for interaction with device drivers. We argue that this hin- ders the development of reliable drivers and thereby under- mines overall system stability. We present an approach to specify driver protocols using a formalism based on state machines. We show that it can simplify device program- ming, facilitate static analysis of drivers against protoc ol specifications, and enable detection of incorrect behaviou rs at runtime.

ABSTRACT Despite the extensive use of caching techniques, the Web is overloaded. While the caching techniques currently used help some, it would be better to use different caching and replication strategies for different Web pages, depending on their characteristics. We propose a framework in which such strategies can be devised independently per Web document. A Web document is constructed as a worldwide, scalable distributed Web object. Depending on the coherence requirements for that document, the most appropriate caching or replication strategy can subsequently be implemented and encapsulated by the Web object. Coherence requirements are formulated from two different perspectives: that of the Web object, and that of clients using the Web object. We have developed a prototype in Java to demonstrate the feasibility of implementing different strategies for different Web objects. Keywords: distributed systems, object replication, object coherence, World-Wide Web, worldwide scalable systems vrije Universiteit Faculty of Mathematics and Computer Science 1 Copyright 1998 IEEE. Published in the Proceedings of ICDCS'98, May 1998 Amsterdam, The Netherlands. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works, must be obtained from the IEEE. Contact: Manager, Copyrights and Permissions / IEEE Service Center / 445 Hoes Lane / P.O. Box 1331 / Piscataway, NJ 08855-1331, USA. Telephone: + Intl. 908-562-3966. 1

In the world of P2P file-sharing things are moving fast. New networks based on new technologies keep appearing, while old ones are slow to disappear. Not only is there growth with regards to the number of networks and the underlying technologies used, but there is also growth in the application of these technologies. Whereas the original growth around P2P networks was based on illegal sharing of content, new (and future) applications tend to focus on legitimate distribution of content. This includes distribution of free software, ...

Different ideas about object-orientation and distributed computing have resulted in a large number of distributed-object models. Use of the same terminology with different meanings makes these models hard to compare. What is currently missing is a framework for describing object models which can be used to compare and classify them. An attempt at defining such a framework is presented in this paper.

Caching and replication techniques can improve latency of the Web, while reducing network traffic and balancing load among servers. However, no single strategy is optimal for replicating all documents. Depending on its access pattern, each document should use the policy that suits it best. This paper presents an architecture for adaptive replicated documents. Each adaptive document monitors its access pattern, and uses it to determine which strategy it should follow. When a change is detected in its access pattern, it re- ...