Over the past decade, hypermedia systems have become increasingly open, distributed, and modular. As a direct result of this, open hypermedia systems have been increasingly successful in providing middleware services such as linking to a large set of clients. This paper presents a new approach to service provision in open hypermedia systems based on the concept of multiple open services. The overall idea with multiple open services is to rethink the way in which services are provided to clients. The goal is to split up services into components, each of which provides a general, scalable, and functionally independent (orthogonal) service. This results in a highly flexible architectural framework that can serve as a vehicle to further investigate many of the open issues relating to open hypermedia systems. The approach can be viewed as a natural next step in the evolution towards more open, distributed, and modular hypermedia systems. The concept of multiple open services is described in detail, and a proof of concept implementation called Construct is presented.

Early hypertext systems were monolithic and closed, but newer systems tend to be open, distributed, and support collaboration. While this development has resulted in increased openness and flexibility, integrating or adapting various different tools, such as content editors, viewers or even other link servers has remained a tedious task. Many developers were implementing essentially similar components, simply for the benefit of having their own platform on which to experiment with hypertexts. The open hypermedia community is addressing this issue of interoperability between open hypermedia systems. The goal of the community is to provide an open hypermedia framework that can be used by application developers outside the community to construct more powerful hypermedia-aware applications. The design and evolution of this framework is presented along with the requirements that drove its development. The framework has matured to the point where it has supported the creation of a number of research prototypes. These prototypes are described and evaluated with respect to their use of the framework.

This paper introduces a project that provides spatial hypermedia services as part of a component-based open hypermedia system (CB-OHS). We focus on the issues of storing both the information space and the parsed spatial structure (for structure sharing purposes) and collaboration support. Continuous re-parsing of spatial structure guarantees consistency between spatial and parsed structure. This promotes parsed structure to first-class status, making persistent storage of it attractive; and, it ensures a consistent view of the parsed structure between collaborative users. For efficiency reasons, the spatial parser is incremental. An accompanying spatial editor shows the validity and utility of the approach. KEYWORDS: open hypermedia system (OHS), component -based open hypermedia system (CB-OHS), collaboration, CSCW, hypermedia middleware, spatial hypermedia, incremental spatial parsing. INTRODUCTION Spatial hypermedia systems support the information analysis domain. In the informati...

Abstract: Researchers in the hypermedia field often lament that the World Wide Web does not support many of hypermedia's rich structuring, navigation and annotation features. What would it take for everyday Web applications to be fully hypermedia compliant, now that the basic hypermedia building blocks exist on the Web? The following four capabilities are the most critical for integrating hypermedia support in the Web environment: edit-capable browsers, storing document content and link anchors separately, external linkbases, and displaying link spans, node and link attributes. Individual developers cannot decide autonomously on how to resolve many of the outstanding issues. Developers need agreed-upon conventions and tools built upon today's Web standards to fully incorporate hypermedia functionality into everyday applications. Categories and Subject Descriptors: H.5.4. [Information interfaces and presentation]

Cooperative work in Extended Enterprises needs a flexible shared workspace for team members to access and manipulate shared information objects in a well-coordinated working process. Current shared workspace systems do not adequately support the evolving character of shared workspaces as needed by Extended Enterprises, i.e. the dynamic cooperation processes, various kinds of shared information contents and the set of cooperative tools. In this paper, the usage scenarios and requirements developed in a European Extended Enterprise project are used to derive the requirements for shared enterprise workspaces. Our approach utilizes component-based cooperative hypermedia to organize shared enterprise workspaces that contain team and process structures, information contents and their corresponding tools. The approach extends classical hypertext models to shared hypermedia objects as well as dynamic bindings between these and the Groupware Components working on them. To demonstrate the approach, a prototype system and a prototypical usage scenario are presented.

Abstract. Digital libraries o er much promise for patrons and many challenges for system designers and implementers. One important issue that faces digital library system designers is the type of support provided to patrons for intellectual work. Although many researchers have noted the desirability of robust hypermedia structuring facilities in digital library systems, this research has tended to focus on navigational hypermedia (primarily used for associative storage and retrieval) only. Many other types of hypermedia, such as spatial, issue-based, and taxonomic, have been ignored. We brie y review some of our experiences with building digital library systems and discuss some of the lessons we learned from our initial prototypes. We then present a scenario of digital library work that illustrates many of the kinds of tasks we have observed users of our systems perform. We use this scenario to suggest a potential area of improvement for current hypermedia support in digital library systems and discuss some of our initial work in this area. Finally, we present some directions of future work and some concluding remarks. 1

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

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Abstract. Many hypermedia models have been proposed, including those specifically developed to model navigational aspects of web sites. But few hypermedia systems have been implemented based on metamodelling principles familiar to the database community. Often there is no clear separation between conceptual and technical issues in the models and their implementations are not based on an explicit representation of a metamodel. This results in a loss of generality and uniformity across systems. Based on principles of metamodel-driven system development, we have implemented a platform that can support various categories of hypermedia systems through the generality and extensibility of the metamodel. We present our metamodel and show how it generalises concepts present in a range of hypermedia and link server systems. 1