In this PhD thesis the question “What makes firms innovative?” is evaluated. In particular, the thesis investigates the differential impact of inter-organizational social networks comprising various different corporate partners on the knowledge stock of a company, evaluates how and to what extent internal knowledge capabilities contribute to innovation success, and scrutinizes how both inter-organizational social networks and internal knowledge capabilities interact and thereby affect innovation success. Therefore, the thesis combines the social capital theory and the concept of absorptive capacity on an organizational level and applies survey data from the German manufacturing industry. Among others, the thesis shows that, first, innovativeness of external partners is contagious, second, that besides customers especially R&D partners can be valuable sources of different types of knowledge, and, third, how the usage of knowledge management systems fosters innovation success. Thereby the results contribute not only to the innovation literature and, in particular, to the open innovation literature, but also to the research fields of inter-organizational knowledge transfer, absorptive capacity, and social capital theory.
Description logics (DLs) represent a widely studied logical formalism with a significant impact in the field of knowledge representation and the Semantic Web. However, they are equipped with a classical descriptive semantics that is characterised by a platonic notion of truth, being insufficiently expressive to deal with evolving and incomplete information, as from data streams or ongoing processes. Such partially determined and incomplete knowledge can be expressed by relying on a constructive semantics. This thesis investigates the model and proof theory of a constructive variant of the basic description logic ALC, called cALC. The semantic dimension of constructive DLs is investigated by replacing the classical binary truth interpretation of ALC with a constructive notion of truth. This semantic characterisation is crucial to represent applications with partial information adequately, and to achieve both consistency under abstraction as well as robustness under refinement, and on the other hand is compatible with the Curry-Howard isomorphism in order to form the cornerstone for a DL-based type theory. The proof theory of cALC is investigated by giving a sound and complete Hilbert-style axiomatisation, a Gentzen-style sequent calculus and a labelled tableau calculus showing finite model property and decidability. Moreover, cALC can be strengthened towards normal intuitionistic modal logics and classical ALC in terms of sound and complete extensions and hereby forms a starting point for the systematic investigation of a constructive correspondence theory.
In times of an ever increasing amount of data and a growing diversity of data types in different application contexts, there is a strong need for large-scale and ﬂexible indexing and search techniques. Metric access methods (MAMs) provide this flexibility, because they only assume that the dissimilarity between two data objects is modeled by a distance metric. Furthermore, scalable solutions can be built with the help of distributed MAMs.
Both IF4MI and RS4MI, which are presented in this thesis, represent metric access methods. IF4MI belongs to the group of centralized MAMs. It is based on an inverted file and thus offers a hybrid access method providing text retrieval capabilities in addition to content-based search in arbitrary metric spaces. In opposition to IF4MI, RS4MI is a distributed MAM based on resource description and selection techniques. Here, data objects are physically distributed. However, RS4MI is by no means restricted to a certain type of distributed information retrieval system. Various application ﬁelds for the resource description and selection techniques are possible, for example in the context of visual analytics. Due to the metric space assumption, possible application fields go far beyond content-based image retrieval applications which provide the example scenario here.
The main objective of this dissertation is to provide theoretical explanations and empirical evidence for the causes and consequences of technostress. The results of this dissertation posit that the IT usage context matters. This means that users perceive technostress when using IT for work and for private purposes; but the causes and consequences differ for both contexts. In the case of using IT for work, technological characteristics and techno-stressors cause employees to feel exhausted at the end of their work day, feel dissatisfied with their job, and develop intentions to quit their job. In the case of IT usage for private purposes, social stressors are identified as new sort of stressor influencing psychological and behavioral strain even more strongly than techno-stressors. Although users of a stressful IT become dissatisfied with its usage and develop intentions to stop using it, the dissertation finds that switching to and using one or more alternatives can be even more stressful. In this context, this dissertation also emphasizes the influence of additional variables, such as user personality on technology characteristics, stressors and strain, concluding that the perception of stressors and strain varies among individuals.
Bearing these conclusions in mind, IT can be seen as a double-edged sword: using IT can be a source of fun, but potentially also a source of stress to others and to ourselves.