Lossy texture compression is increasingly used to reduce GPU memory and bandwidth consumption. However, as raised by recent studies, evaluating the quality of compressed textures is a difficult problem. Indeed using Peak Signal-to-Noise Ratio (PSNR) on texture images, like done in most applications, may not be a correct way to proceed. In particular, there is evidence that masking effects apply when the texture image is mapped on a surface and combined with other textures (e.g., affecting geometry or normal). These masking effects have to be taken into account when compressing a set of texture maps, in order to have a real understanding of the visual impact of the compression artifacts on the rendered images. In this work, we present the first psychophysical experiment investigating the perceptual impact of texture compression on rendered images. We explore the influence of compression bit rate, light direction, and diffuse and normal map content on the visual impact of artifacts. The collected data reveal huge masking effects from normal map to diffuse map artifacts and vice versa, and reveal the weakness of PSNR applied on individual textures for evaluating compression quality. The results allow us to also analyze the performance and failures of image quality metrics for predicting the visibility of these artifacts. We finally provide some recommendations for evaluating the quality of texture compression and show a practical application to approximating the distortion measured on a rendered 3D shape.

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Service management has been a hot topic in the research community for the last couple of years. However, due to the complexity of this research area, no commonly accepted definition of the terms service, service management, and the associated management tasks has evolved yet. This paper contributes to the ongoing process of defining these terms by proposing a top-down oriented and systematic methodology that is used to analyze and identify the necessary actors and the corresponding inter- and intra-organizational relationships. Then, a generic service model is introduced that defines commonly needed service-related terms, concepts and structuring rules in a general and unambiguous way. Since most of the work that is being presented here is still in flux, the service model is finally used to identify and structure open research questions.

Customer service management (CSM) offers a management interface between customers and a service provider, which enables the customers to individually monitor and control their subscribed service. Introducing CSM in the service provider's environment includes communicating and interacting with its service management. Considering the complexity of service management, the goal of this paper is to logically separate CSM and service management, from an enterprise point of view, by identifying specific CSM roles which describe the functions of service management that are relevant for CSM. By using the concepts of roles and associations, we abstract from the details of the underlying service management and identify the requirements that have to be met by the service management. The specific CSM roles and associations are formalized using the terms and concepts of the ODP (open distributed processing) enterprise viewpoint specification in order to ensure that the resulting specification can be applied to a wide range of scenarios. The instantiation of the proposed approach within a real-life scenario shows the applicability and the benefits of our approach.

Customer service management (CSM) offers a management interface between customer and service provider which enables customers to individually monitor and control their subscribed service. This paper presents an approach towards the definition, implementation and instantiation of a CSM management information base for an IP connectivity service (CSM-IP-MIB). The approach uses object-oriented techniques to model the CSM-IP-MIB in order to facilitate reusability and specialization in real-life scenarios. The CSM-IP-MIB consists of four packages that reflect the relevant details of the IP connectivity service, including contracts, SLA, topology, current and historical state of the IP connectivity, QoS parameters, QoS violations and problem management as well as authentication and access control to provide customer-specific views. The CSM-IP-MIB is implemented using the CORBA technology, resulting in a distributed client/server application, which is being instantiated for the IP connectivity service of the German Research Network Organization.