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A key challenge for dynamic Web service selection is that Web services are typically highly configurable and service requesters often have dynamic preferences on service configurations. Current approaches, such as WS-Agreement, describe Web services by enumerating the various possible service configurations, an inefficient approach when dealing with numerous service attributes with large value spaces. We model Web service configurations and associated prices and preferences more compactly using utility function policies, which also allows us to draw from multi-attribute decision theory methods to develop an algorithm for optimal service selection. In this paper, we present an OWL ontology for the specification of configurable Web service offers and requests, and a flexible and extensible framework for optimal service selection that combines declarative logic-based matching rules with optimization methods, such as linear programming. Assuming additive price/preference functions, experimental results indicate that our algorithm introduces an overhead of only around 2 sec. compared to random service selection, while giving optimal results. The overhead, as percentage of total time, decreases as the number of offers and configurations increase.

We report on the characteristics of an active fiber with core material made by sintering of Yb-doped silica powders as an alternative to a conventional modified chemical vapor deposition (MCVD) technique. This material provides the possibility to design very large and homogenously rare-earth doped active fiber cores. We have determined a fiber background attenuation of 20 dB/km and measured a slope efficiency of 80%. These values are comparable to established fibers made by MCVD technology.

In this paper, we present a demonstrator system which applies semantic web services technology to business-to-business integration, focussing specifically on a logistics supply chain. The system is able to handle all stages of the service lifecycle -discovery, service selection and service execution. One unique feature of the system is its approach to protocol mediation, allowing a service requestor to dynamically modify the way it communicates with aprovider, based on a description of the provider's protocol. We present the architecture of the system, together with an overview of the key components (discovery and mediation) and the implementation.

The increasing fields of applications for modern optical fibers present great challenges to the material properties and the processing technology of fiber optics. This paper gives an overview of the capabilities and limitations of established vapor deposition fiber preform technologies, and discusses new techniques for improved and extended doping properties in fiber preparation. In addition, alternative fabrication technologies are discussed, such as a powder-based process (REPUSIL) and an optimized glass melting method to overcome the limits of conventional vapor deposition methods concerning the volume fabrication of rare earth (RE)-doped quartz and high silica glasses. The new preform technologies are complementary with respect to enhanced RE solubility, the adjustment of nonlinear fiber properties, and the possibility of hybrid fiber fabrication. The drawing technology is described based on the requirements of specialty fibers such as adjusted preform and fiber diameters, varying coating properties, and the microstructuring of fiber configurations as low as in the nanometer range.

In binary aluminosilicate liquids and glasses, heterogeneity on intermediate length scale is a crucial factor for optical fiber performance, determining the lower limit of optical attenuation and Rayleigh scattering, but also clustering and precipitation of optically active dopants, for example, in the fabrication of high-power laser gain media. Here, we consider the low-frequency vibrational modes of such materials for assessing structural heterogeneity on molecular scale. We determine the vibrational density of states VDoS g(ω) using low-temperature heat capacity data. From correlation with low-frequency Raman spectroscopy, we obtain the Raman coupling coefficient. Both experiments allow for the extraction of the average dynamic correlation length as a function of alumina content. We find that this value decreases from about 3.9 nm to 3.3 nm when mildly increasing the alumina content from zero (vitreous silica) to 7 mol%. At the same time, the average inter-particle distance increases slightly due to the presence of oxygen tricluster species. In accordance with Loewensteinian dynamics, this proves that mild alumina doping increases structural homogeneity on molecular scale.

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