The World Wide Web has succeeded in large part because its software architecture has been designed to meet the needs of an Internet-scale distributed hypermedia system. The Web has been iteratively developed over the past ten years through a series of modifications to the standards that define its architecture. In order to identify those aspects of the Web that needed improvement and avoid undesirable modifications, a model for the modern Web architecture was needed to guide its design, definition, and deployment. Software architecture research investigates methods for determining how best to partition a system, how components identify and communicate with each other, how information is communicated, how elements of a system can evolve independently, and how all of the above can be described using formal and informal notations. My work is motivated by the desire to understand and evaluate the architectural design of network-based application software through principled use of architectural constraints, thereby obtaining the functional, performance, and social properties desired of an architecture. An architectural style is a named, coordinated set of architectural constraints. This dissertation defines a framework for understanding software architecture via architectural styles and demonstrates how styles can be used to guide the architectural design of network-based application software. A survey of architectural styles for network-based applications is used to classify styles according to the architectural properties they induce on an architecture for distributed hypermedia. I then introduce the Representational State Transfer (REST) architectural style and describe how REST has been used to guide the design and development of the architecture for the modern Web. REST emphasizes scalability of component interactions, generality of interfaces, independent deployment of components, and intermediary components to reduce interaction latency, enforce security, and encapsulate legacy systems. I describe the software engineering principles guiding REST and the interaction constraints chosen to retain those principles, contrasting them to the constraints of other architectural styles. Finally, I describe the lessons learned from applying REST to the design of the Hypertext Transfer Protocol and Uniform Resource Identifier standards, and from their subsequent deployment in Web client and server software.

The World Wide Web has succeeded in large part because its software architecture has been designed to meet the needs of an Internet-scale distributed hypermedia application. The modern Web architecture emphasizes scalability of component interactions, generality of interfaces, independent deployment of components, and intermediary components to reduce interaction latency, enforce security, and encapsulate legacy systems. In this article we introduce the Representational State Transfer (REST) architectural style, developed as an abstract model of the Web architecture and used to guide our redesign and definition of the Hypertext Transfer Protocol and Uniform Resource Identifiers. We describe the software engineering principles guiding REST and the interaction constraints chosen to retain those principles, contrasting them to the constraints of other architectural styles. We then compare the abstract model to the currently deployed Web architecture in order to elicit mismatches between the existing protocols and the applications they are intended to support.

The Internet has led to an increase in the quantity and diversity of information available for searching. Furthermore, users

Resource Discovery is the term commonly used to refer to the exercise of locating, accessing, retrieving, and managing relevant resources (eg information and services) for a user from widely distributed heterogeneous networks. The Resource Discovery Unit of the Research Data Network Cooperative Research Centre is working on tools and technologies which make these tasks easier in the Open Information Locator (OIL) project. This paper aims to present and discuss some of the central issues in the area of Resource Discovery that the OIL project is addressing. It also aims to position the OIL project with respect to related research fields including Information Retrieval, Distributed Databases, and Digital Libraries. 1 Global Resource Discovery 1.1 Resource Discovery: a definition Resource Discovery is a multidisciplinary domain (as shown in Figure 1). Researchers in each of these disciplines have differing views on what resource discovery is. The resulting polysemic definition of resourc...

This paper deals with current (conceptual) issues in the field of contract management. We describe a basic contract life cycle with four phases: offer placement, offer confirmation (conclusion of the contract), fulfillment of duties (consumption of rights), and contract archiving. In our investigation of contract content, we identify core contract objects, usage-specific extension objects and their relationships. On the basis of various usage scenarios for digital contracts, we proceed to introduce an approach for scenario-specific contract composition (Phases 1 and 2 of the contract life cycle). Addressing phase 3 of the contract life cycle (fulfillment of digital contracts), we distinguish digital contracts from electronic tickets, and finally envisage the consumption of usage rights by means of electronic tickets. 1

(DSTC Tech Report 34) Resource Discovery is the term commonly used to refer to the exercise of locating, accessing, retrieving, and managing relevant resources (eg information and services) for a user from widely distributed heterogeneous networks. The Resource Discovery Unit of the Research Data Network Cooperative Research Centre is working on tools and technologies which make these tasks easier in the Open Information Locator (OIL) project. This paper aims to present and discuss some of the central issues in the area of Resource Discovery that the OIL project is addressing. It also aims to position the OIL project with respect to related research fields including Information Retrieval, Distributed Databases, and Digital Libraries. 1 Global Resource Discovery 1.1 Resource Discovery: a definition Resource Discovery is a multidisciplinary domain (as shown in Figure 1). Researchers in each of these disciplines have differing views on what resource discovery is. The resulting polysemi...

Abstract. The eXtensible Markup Language (XML) opens the possibilityto start anew, on a solid technological ground, the ambitious goal of developing a suitable technologyfor the creation and maintenance of a virtual, distributed, hypertextual library of formal mathematical knowledge. In particular, XML provides a central technologyfor storing, retrieving and processing mathematical documents, comprising sophisticated web-publishing mechanisms (stylesheets) covering notational and stylistic issues. Bythe application of XML technologyto the large repositories of structured, content oriented information offered byLogical Frameworks we meet the ultimate goal of the Semantic Web, that is to allow machines the sharing and exploitation of knowledge in the Web way, i.e. without central authority, with few basic rules, in a scalable, adaptable, extensible manner. 1

This document is an Internet-Draft. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as ‘‘work in progress.’’ To learn the current status of any Internet-Draft, please check the ‘‘1id-abstracts.txt’ ’ listing contained in the Internet-Drafts Shadow Directories on ftp.is.co.za (Africa), nic.nordu.net (Europe), munnari.oz.au (Pacific Rim), or ftp.isi.edu (US West Coast). This memo documents requirements for listing directory services schema in a centrally operated, administered, and maintained

This paper describes the Harvest Broker. The Broker plays a central role in the Harvest Query Manager Broker Storage Manager and Indexer Collector Client Object Cache Replication Manager Provider Gatherer 1. search object & retrieve 2. methods access SOIF SOIF Registry Broker Figure 1.1: The Harvest Architecture. architecture. It maintains a dynamic SOIF object database and presents this data to users through a powerful and effective query interface. For the purpose of characterizing access patterns, the Broker is instrumented to collect statistics through a selective logging facility. The Broker also supports real-time administrative control so that administrators can dynamically configure Broker parameters to best fit the environment. 1.1 Components

The system Progress facilitates the easy provision and usage of computational services via the INTERNET. Moreover, it offers powerful value added services in this area. The concept of plans can be used to combine computational services located at different hosts to more powerful services. In this article, we demonstrate how this concept can be coupled with other INTERNET technologies like Java to achieve a visual programming environment for large-scale INTERNET programming. 1. Introduction Over the last years, a lot of new technologies have been developed to use computational services (programs or algorithms) via networks and in particular via the INTERNET. While Java, ActiveX, and Javascript may be the most important technologies for client-side computing, server-side computing can be handled with CGI, Java RMI, CORBA [11, 9], and RPC [6]. With the system Progress [1, 3, 2], which we have developed, we follow similar aims like the above mentioned technologies for server-side computi...