Siegfried Reich

FOHM: a fundamental open hypertext model for investigating interoperability between hypertext domains

The Open Hypermedia Systems community has been largely concerned with interoperability between hypertext systems which share the same paradigm. It has evolved a component based framework for this purpose, in which specific but incompatible middleware components are designed for each hypertext domain, such as navigational hypertext, spatial hypertext or taxonomic hypertext. This paper investigates the common features of these domains and introduces FOHM, a Fundamental Open Hypertext Model, which defines a common data model and set of related operations that are applicable for all three domains. Using this layer the paper explores the possible semantics of linking between different hypertext domains, and shows that each can introduce features which benefit the other domains.

Addressing Interoperability in Open Hypermedia: the Design of the Open Hypermedia Protocol

Abstract 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, integration or adaptation of various different tools (such as content editors, viewers, services, 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 this effort is to provide an open 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 researc...

Interoperability between hypermedia systems: the standardisation work of the OHSWG

CONTENTS OF THE TECHNICAL BRIEFING The Open Hypermedia Systems Working Group (OHSWG) was formed at the second workshop on open hypermedia systems (OHS), held in April, 1996, in Washington, DC, in conjunction with the 1996 ACM Conference on Hypertext. The original purpose of defining an open hypermedia protocol for OHS clients has evolved into an effort to standardise general hypermedia systems work. This broader effort is driven by the desire to maximise the applicability of the last decade of hypermedia systems and infrastructure research.

Hypermedia: Openness, Structural Awareness, and Adaptivity

The task of information integration challenges software engineers on a daily basis. Software artifacts, produced during software development, contain many implicit and explicit relationships whose sheer numbers quickly overwhelm a software team’s ability to understand, manipulate, and evolve them. We are developing an information integration environment to aid software engineers in tackling this difficult task and are making use of open hypermedia techniques to enable critical characteristics of the environment, such as third-party tool integration, typed links, and a partitioned information space through the use of contexts, traditionally referred to as composites. We describe our prototype implementation of the information integration environment, focusing on how open hypermedia has either influenced the design of the environment, or contributed directly to its functional capabilities.

Connecting Databases to the Web: A Taxonomy of Gateways

The increasing popularity of the World-Wide Web (WWW) has resulted in a growing interest of companies to make use of the Internet for marketing, selling and presentation purposes. Moreover, with evolving Intranets, there is also a rising demand in using the Web for core business applications. Given the fact that databases are used in many business areas as information repositories, the idea of combining easy to use user interfaces as provided by the World-Wide Web browsers with state-of-the-art data management facilities as supported by todays database management facilities appears to be promising. However, there exist a variety of different technical solutions for connecting databases to the Web, each of them having its strengths and weaknesses with respect to criteria of the individual application domains.

A development environment for building component-based open hypermedia systems

The Construct development environment is targeted at the construction of different types of hypermedia services. The primary goal of the environment is to ease the construction of component-based open hypermedia systems by providing development tools that assist the system developers in the generation of the set of services that make up a hypermedia system.

Why GPS makes distances bigger than they are

ABSTRACT Global navigation satellite systems such as the Global Positioning System (GPS) is one of the most important sensors for movement analysis. GPS is widely used to record the trajectories of vehicles, animals and human beings. However, all GPS movement data are affected by both measurement and interpolation errors. In this article we show that measurement error causes a systematic bias in distances recorded with a GPS; the distance between two points recorded with a GPS is – on average – bigger than the true distance between these points. This systematic ‘overestimation of distance’ becomes relevant if the influence of interpolation error can be neglected, which in practice is the case for movement sampled at high frequencies. We provide a mathematical explanation of this phenomenon and illustrate that it functionally depends on the autocorrelation of GPS measurement error (C). We argue that C can be interpreted as a quality measure for movement data recorded with a GPS. If there is a strong autocorrelation between any two consecutive position estimates, they have very similar error. This error cancels out when average speed, distance or direction is calculated along the trajectory. Based on our theoretical findings we introduce a novel approach to determine C in real-world GPS movement data sampled at high frequencies. We apply our approach to pedestrian trajectories and car trajectories. We found that the measurement error in the data was strongly spatially and temporally autocorrelated and give a quality estimate of the data. Most importantly, our findings are not limited to GPS alone. The systematic bias and its implications are bound to occur in any movement data collected with absolute positioning if interpolation error can be neglected.

Web Engineering – Old Wine in New Bottles?

Modern Web applications are full-fledged, complex software systems. Therefore, the development of Web applications requires a methodologically sound engineering approach called Web Engineering. It is not clear, however, to which extent existing solutions from relevant areas, most notably software engineering can be reused as such for the development of Web applications and consequently, if Web Engineering is really a discipline on its own. This paper highlights the characteristics of Web application development as found in existing literature thus providing a prerequisite for analyzing the appropriateness of existing engineering solutions. The characteristics are categorized according to four dimensions, comprising the software product itself, its development, its use and evolution as a cross-cutting concern.

Naming as a fundamental concept of open hypermedia systems

Names play a key role in distributed hypertext systems, for two main reasons: Firstly, because accessing and managing system services require finding and locating the relevant components. Secondly, because managing structures between hypertext resources, such as nodes, anchors and links, requires that these resources are named and addressed. We argue that naming services are endemic to hypertext systems and therefore, form a core part of any hypertext system’s infrastructure. In particular, the current move towards interoperable component-based Open Hypermedia Systems (CB-OHS) demonstrates the need for naming components.

Offering open hypermedia services to the WWW: a step-by-step approach for developers

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.