Hypermedia systems and more specifically open hypermedia systems (OHS) provide a rich set of implementations of different hypertext flavors such as navigational hypertext, spatial hypertext or taxonomic hypertext. Additionally, these systems offer component-based modular architectures and address interoperability between hypertext domains. Despite multiple efforts of integrating Web clients, a widespread adoption of OHS technology by Web developers has not taken place. In this paper it is argued that Web Services- which offer a component model for Web applications- can be integrated in OHSs. An architectural integration is proposed, a step-by-step process is outlined and an example of integration is provided. This very approach is aimed to benefit both worlds: the Web community with new rich hypermedia functionality that extends the current navigational hypermedia, and the OHS community by opening its tools and platforms to the many developer groups of the Web community.

This paper discusses a new hypermedia-based model known as IUHM. IUHM emerged as a result of the development of the OPALES system, a collaborative environment for exploring and indexing video archives in a digital library. A basic design requirement of OPALES is that it must permit and support the integration of new services throughout its life cycle. Thus, IUHM depends heavily upon the notions of extensibility and openness. Support for

Structural computing provides techniques and tools to ease the task of developing application infrastructure; infrastructure that provides common services such as persistence, naming, distribution, navigational hypermedia, etc., over a set of application-specific or domain-specific structures. Within structural computing, "structure" refers to a combination of data and relationships over that data. Structure servers support the specification and manipulation of structures. One important aspect of structural computing is the power and flexibility it provides application developers in constructing new applications. A large part of this power is due to structural computing's ability to provide awareness services over both structure and behavior. We define this concept and describe the awareness services provided by the Themis structural computing environment. The utility of these services are demonstrated by presenting the impact they have had on the InfiniTe information integration environment. In particular, these services help to increase the e#ciency and reduce the size of domain-specific applications built using structural computing technology. We conclude by discussing how these services might influence the open hypermedia field and the development of new hypermedia services.

This paper takes a first step towards defining a standard component -based open hypermedia system storage interface in the context of the Open Hypermedia System Working Group. The paper presents a proposal for the core set of services of such an interface. The existence of such an interface is one of the basic preconditions for interoperability at the middleware level in hypermedia systems. The proposed interface has been implemented both as a stand-alone hypermedia storage service and as a basic service in the Construct development environment. Both implementations are in Java and are based on underlying file system services.

A major goal of this research is to present a framework for discussing issues and questions around Web Information Systems (WIS). WIS dynamically generate their contents, and thus require some mechanism to automatically infer metadata about WIS objects, infer access to relationships (i.e., links) among information objects, and provide hypermedia functionality such as annotation and ad hoc (userdeclared) linking. The framework focuses on integrating information systems into the Web and providing hypermedia functionality to them. This should result in new ways to view and manage the WIS' knowledge and information relationships. The framework has three layers: interface, integration and infrastructure. The interface layer highlights the importance of designing Web interfaces appropriate for system functionality. The integration layer concerns integrating information systems, hypermedia support and inter-application interoperability. The infrastructure layer concerns using the Internet and Web technologies to support interoperability, hypermedia, and overall development at the integration layer. This framework should help system developers think more fully about their designs. 1.

This paper argues that the existence of a developer support framework is a critical issue to the usage of Open Hypermedia Systems (OHSs). For this reason, the OHS Community would benefit by the adoption of both a service discovery mechanism and a set of standards and tools to approach the development of hypermedia clients in a transparent and methodological manner.

Abstract: There is an increasing number of different ways to represent knowledge structures on computers. Additionally, people want to use different devices, applications, or media for the same knowledge structures. To support this, we investigate structure interoperability, including transformation of structures and combination of different structure types. Our work focuses on structuring tasks using paper as well as those using computers. Our overall goal is to improve the usage of computers as tools for structuring knowledge work.

Web applications make increasingly use of services that are provided by external information systems to deliver advanced functionalities to end users. However, many issues regarding how these services are integrated into web applications and how service oriented web applications evolve, are reengineered and refactored are still addressed in an ad hoc manner. In this paper, we present how design patterns can lessen the efforts required to integrate hypermedia services into web applications. In particular we present how evolution and maintenance issues are addressed within Callimachus, a CB-OHS that web applications need to integrate in order to provide hypertext functionality to end users.

The field of structural computing is working to produce techniques and tools to ease the task of developing application infrastructure. This paper describes the Themis structural computing environment. Themis provides developers with a generic structure server and two key extension mechanisms that enable the rapid creation of tools for a variety of application domains. The two novel extension mechanisms enable support for structure templates and automated structure transformation. Each of these mechanisms is described in detail along with the interfaces and capabilities of the generic structure server. We evaluate the utility of Themis in supporting the migration of the InfiniTe information integration environment from an XML-based repository to the Themis structure server. The use of Themis has led to a significant reduction in the number of lines of code required to produce the InfiniTe prototype. In addition, the higher level of abstraction provided by Themis has led to code that is easier to understand and maintain than the XML-based code it replaces. The paper concludes with a discussion of how structural computing tools, such as Themis, can impact software engineering and software engineering research. 1