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Polycomb Repressive Complex (PRC) 2 catalyzes the H3K27me3 modification that warrants inheritance of a repressive chromatin structure during cell division, thereby assuring stable target gene repression in differentiated cells. It is still under investigation how H3K27me3 is passed on from maternal to filial strands during DNA replication; however, cell division can reinforce H3K27me3 coverage at target regions. To identify novel factors involved in the Polycomb pathway in plants, we performed a forward genetic screen for enhancers of the like heterochromatin protein 1 (lhp1) mutant, which shows relatively mild phenotypic alterations compared with other plant PRC mutants. We mapped enhancer of lhp1 (eol) 1 to a gene related to yeast Chromosome transmission fidelity 4 (Ctf4) based on phylogenetic analysis, structural similarities, physical interaction with the CMG helicase component SLD5, and an expression pattern confined to actively dividing cells. A combination of eol1 with the curly leaf (clf) allele, carrying a mutation in the catalytic core of PRC2, strongly enhanced the clf phenotype; furthermore, H3K27me3 coverage at target genes was strongly reduced in eol1 clf double mutants compared with clf single mutants. EOL1 physically interacted with CLF, its partially redundant paralog SWINGER (SWN), and LHP1. We propose that EOL1 interacts with LHP1-PRC2 complexes during replication and thereby participates in maintaining the H3K27me3 mark at target genes.

Managing security in distributed systems requires flexible and expressive authorisation models with support for conflict resolution. Models need to be hierarchical but also non-monotonic supporting both positive and negative authorisations. In this paper, we present an approach to resolve the authorisation conflicts that inevitably occur in such models, with administrator specified conflict resolution strategies (rules). Strategies can be global or applied to specific parts of a system and dynamically loaded for different applications. We use Courteous Logic Programs (CLP) for the specification and enforcement of strategies. Authorisation policies are translated into labelled rules in CLP and prioritised. The prioritisation is regulated by simple override rules specified or selected by administrators. We demonstrate the capabilities of the approach by expressing the conflict resolution strategy for a moderately complex authorisation model that organises subjects and objects hierarchically.

A distributed reasoning platform is presented to reduce the energy consumption of Wireless Sensor Networks (WSNs) o ering geospa- tial services by minimizing the amount of wireless communication. It combines local, rule-based reasoning on the sensors and gateways with global, ontology-based reasoning on the back-end servers. The Seman- tic Sensor Network (SNN) Ontology was extended to model the WSN energy consumption. One exemplary prototype is presented, namely the Garbage Bin Tampering Monitor (GBTM).

The popularity of multimedia services has resulted in new revenue opportunities for network and service providers but has also introduced important new challenges. The large amount of resources and stringent quality requirements imposed by multimedia services has triggered the need for open content aware networks, where specific management algorithms that optimize the delivery of multimedia services can be dynamically plugged in when required. In the past, a plethora of algorithms have been proposed ranging from specific cache algorithms to video client heuristics that are optimized for a specific multimedia service type and its corresponding delivery. However, it remains difficult to accurately characterize the performance of these algorithms and investigate the impact of an actual deployment in multimedia services. In this paper, we present a framework that allows evaluating the performance of such algorithms for open content aware networks. The proposed evaluation framework has two important advantages. First, it performs an emulation of the novel algorithms instead of using a simulation approach, which is often carried out to characterize performance. Second, the emulation framework allows evaluating the impact of combining different multimedia algorithms with each other. We present the architecture of the emulation framework and discuss the main software components used. Furthermore, we present a performance evaluation of an illustrative use case, which identifies the need for emulation-based evaluation.

HTTP Adaptive Streaming (HAS) is becoming the de-facto standard for Over-The-Top video streaming services. Video content is temporally split into segments which are offered at multiple qualities to the clients. These clients autonomously select the quality layer matching the current state of the network through a quality selection heuristic. Recently, academia and industry have begun evaluating the feasibility of adopting layered video coding for HAS. Instead of downloading one file for a certain quality level, scalable video streaming requires downloading several interdependent layers to obtain the same quality. This implies that the base layer is always downloaded and is available for playout, even when throughput fluctuates and enhancement layers can not be downloaded in time. This layered video approach can help in providing better service quality assurance for video streaming. However, adopting scalable video coding for HAS also leads to other issues, since requesting multiple files over HTTP leads to an increased impact of the end-to-end delay and thus on the service provided to the client. This is even worse in a Live TV scenario where the drift on the live signal should be minimized, requiring smaller segment and buffer sizes. In this paper, we characterize the impact of delay on several measurement-based heuristics. Furthermore, we propose several ways to overcome the end-to-end delay issues, such as parallel and pipelined downloading of segment layers, to provide a higher quality for the video service.

The patient room of the future would be able to sense the needs and preferences of the patients and nurses and adapt itself accordingly by combining all the heterogeneous data offered by the different technologies. This goal can be achieved by developing a context-aware framework, which exploits and integrates the heterogeneous data by utilizing a continuous care ontology. The existing ontology engineering methodologies are rather extreme in their choices to include domain experts. On the one hand, there are methodologies that only discuss the scope, use and requirements of the ontology with the domain experts. On the other hand, there are approaches in which the ontology is completely constructed by the domain experts by providing them with user-friendly and collaborative tools. In this paper, a participatory ontology engineering methodology is presented that finds a middle ground between these two extremes. The methodology actively involves social scientists, ontology engineers and stakeholders. The stakeholders participate in each step of the ontology life cycle without having to construct the ontology themselves or attribute a large amount of their time. The applicability of the methodology is illustrated by presenting the co-created continuous care ontology.

Dependable performance measurement is a common requirement for all on-line services. The ongoing tendency to outsource not only infrastructure, but also software parts to several suppliers, creates a new challenge to providers. Traditional solutions cannot easily monitor service performance as perceived by end users, since providers do not have control over all hardware/software involved. Our research focuses on evaluating how data passively collected from network devices can be used to verify end-to-end service performance. Our goal is to compare this approach with current methods used to monitor distributed services. Given the constant mutation of applications on the Internet, as well as the fast increase of the number of users, we are looking for flexible and scalable solutions.

ispartof: pages:123-131 ispartof: Digital Television Revisited. Linking Users, Markets and Policies. Workshop proceedings, COST Action 298 ‘Participation in the Broadband Society’. pages:123-131 ispartof: COST Action 298 ‘Participation in the Broadband Society’ location:Budapest status: published

As the variety in network service platforms and end user devices grows rapidly, content providers must constantly adapt their production system to support these new technologies. A factor that highly complicates this process is the need for interactivity. In the Multimedia Content Distribution Platform (MCDP) Project, an architecture for deploying highly interactive and synchronised television programs over a diverse collection of broadcast networks and end user devices was developed. It consists of a middleware platform with pluggable support for new broadcast networks and end-user devices, whilst preserving synchronised interactivity. In order to support a maximum of functionality and use cases; downloadable applications are used to provide the interactive services. As the user interface of such applications may vary depending on the capabilities of the different target devices, the MCDP middleware uses UIML for the description of generic user interfaces: The MCDP middleware is also used as the main platform for the delivery of synchronized, interactive services in a IP Datacasting system combining DVB-H and UMTS.