I. Kuz

Differentiated strategies for replicating Web documents

Replicating Web documents reduces user-perceived delays and wide-area network traffic. Numerous caching and replication protocols have been proposed to manage such replication while keeping the document copies consistent. We claim, however, that no single caching or replication policy can efficiently manage all documents. Instead, we propose that each document be replicated with a policy specifically tailored to it. We have collected traces on our universitys Web server and conducted simulations to determine the performance such tailored policies would produce, as opposed to using the same policy for all documents. The results show a significant performance improvement with respect to end-user delays, wide-area network traffic and document consistency. We also present how these results can be used to build adaptive replicated Web documents, capable of automatically selecting the policy that best suits them.

A framework for consistent, replicated Web objects

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.

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 not only encapsulate state and operations, but also the policy by which its state is distributed, cached, replicated, migrated, etc.

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 globe infrastructure directory service

To implement adaptive replication strategies for Web documents, we have developed a wide-area resource management system. This system allows servers to be managed on a local and global level. On a local level the system manages information about the resources and services provided by the servers, while on a global level the system allows servers to be searched for, added to, and removed from the system. As part of the system, and also in order to implement adaptive replication strategies, we introduce a hierarchical location representation for network elements such as servers, objects, and clients. This location representation allows us to easily and efficiently find and group network elements based on their location in a worldwide network. Our resource management system can be implemented using standard Internet technologies and has a broader range of applications besides making adaptive replication strategies possible for Web documents.

Securely replicated Web documents

In order to achieve better scalability and reduce latency in handling user requests, many Web applications make extensive use of data replication through caches and content delivery networks. However, in such scenarios data is often placed on untrusted hosts. As a result, existing replication mechanisms open a wide class vulnerabilities, ranging from denial of service to content masquerading. 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.

A distributed-object infrastructure for corporate Websites

A corporate Web site is the virtual representation of a corporation or organization on the Internet. Corporate Web sites face numerous problems due to their large size and complexity, and the nonscalability of the underlying Web infrastructure. Current solutions to these problems generally rely on traditional scaling techniques such as caching and replication. These are usually too restrictive, however taking a one-size-fits-all approach and applying the same solution to every document. We propose Globe as a foundation upon which to build scalable corporate Web sites, and introduce GlobeDoc, a Web site model based on Globe distributed shared objects. The paper describes GlobeDoc, highlighting the design and technical details of the infrastructure.