Tobias Heide

Can We Afford Integrity by Proof-of-Work? Scenarios Inspired by the Bitcoin Currency

Proof-of-Work (PoW), a well-known principle to ration resource access in client-server relations, is about to experience a renaissance as a mechanism to protect the integrity of a global state in distributed transaction systems under decentralized control. Most prominently, the Bitcoin cryptographic currency protocol leverages PoW to (1) prevent double spending and (2) establish scarcity, two essential properties of any electronic currency. This chapter asks the important question whether this approach is generally viable. Citing actual data, it provides a first cut of an answer by estimating the resource requirements, in terms of operating cost and ecological footprint, of a suitably dimensioned PoW infrastructure and comparing them to three attack scenarios. The analysis is inspired by Bitcoin, but generalizes to potential successors, which fix Bitcoin’s technical and economic teething troubles discussed in the literature.

Dynamic Knowledge Mapping: A Visualization Approach for Knowledge Management Systems

Visualizing the contents of knowledge management systems allows for better comprehensibility of the knowledge base, gives a condensed overview, and provides entry points to particular knowledge items. In this context, two different visualization approaches have been proposed in the literature. On the one hand, algorithm-based approaches have been introduced, which are capable of automated generation of reproducible visualizations. On the other hand, visualizations such as knowledge maps have to be created individually by domain experts. In this paper, we propose a combined approach of dynamic knowledge mapping, which is based on a manual creation of the underlying context (e.g., the metaphor) of the visualization. The particular knowledge items, however, are mapped onto this background automatically in response to changes in the knowledge base. Thus, our approach benefits from the use of a challenging graphical context while allowing for an automated generation of visualizations.

A METHOD FOR MEASURING USER PREFERENCES IN INFORMATION SYSTEMS DESIGN CHOICES

Information System Design (ISD) applies information technology to achieve desired ends in organizations and implies many technology choices to be made. A successful design of information systems addresses the different views of all its stakeholders in these decisions. If we consider that sub-part of an IS that is intended to assist in customer processes, a purposeful assessment of the preferences of this anonymous mass is needed. Methods of Human-Centered ISD are not sufficient in that case for that they require too close integration of the subjects; and state of the art preference measurement techniques are likely to be too time-consuming and cognitively challenging if the number of alternatives is large. Building on the Q-Methodology, originally developed to reveal subjectivity in psychology, we suggest a novel method for user preference measurement. We report on a case in which we failed by applying standard techniques for user measurement, but succeeded with Q-Sort. By means of an experiment we subsequently compare the mentioned methods and identify root causes for failure and success we experienced in the case, which for Q-Sort include short execution time, measuring many design choices at one time, satisfaction of the interviewees, and an effective IT support.

Fostering Comparability in Content Management Using Semantic Standardization

This chapter addresses the lack of consistency and comparability in content management. We provide a solution to this problem and propose a conceptual specification of a generic portal structure that allows for semantic standardization of content. The structure and semantics of textual descriptions must be customized for given application scenarios, so we demonstrate such a customization for an exemplary research portal. In the example we address design science research and describe a research process that uses the customized portal definition. We conclude that our approach can increase the consistency and comparability of content in general through (1) an individually customizable system structure that reflects the nature of a specific application scenario better than generic structures can and (2) a semantic standardization of textual descriptions that forces the portal users to be precise and compact in their descriptions and to consistently apply the vocabulary of the domain.