Graph drawing and visualization represent structural information as diagrams of abstract graphs and networks. An important subset of graphs is directed acyclic graphs (DAGs). E-Spring algorithm, extended from the popular spring embedder model, eliminates node overlaps in clustered DAGs by modeling nodes as charged particles whose repulsion is controlled by edges modeled as springs. The drawing process needs to reach a stable state when the average distances of separation between nodes are near optimal. This paper presents an enhancement to E-Spring to introduce a stopping condition, which reduces equilibrium distances between nodes and therefore results in a significantly reduced area for DAG visualization. It imposes an upper bound on the repulsive forces between nodes based on graph geometry. The algorithm employs node interleaving to eliminate any residual node overlaps. These new techniques have been validated by visualizing eBay buyer-seller relationships and resulted in overall area reductions in the range of 45% to 79%.
Abstract. Graph drawing and visualization represent structural information as diagrams of abstract graphs and networks. E-Spring Algorithm, derived from the popular spring embedder model, was proposed to eliminate node overlaps in the drawings of clustered directed acyclic graphs Gc. In this paper, we apply the E-Spring algorithm to general graphs by minimizing edge-node intersections. Initially, a tree structure is extracted from the original graph using the breadth-first search (BFS) algorithm. The extracted tree is then visualized without node overlaps using the E-Spring algorithm, and the remaining non-tree edges are appended to this visualization. A post-processing step that implements edge routing is performed on the obtained visualization to eliminate residual edge-node intersections. This method has been validated by visualizing eBay buyer-seller relationships and Graph Catalog benchmarking data.
QoS (Quality of Service) provisioning is an important factor that determines the success of any software service deployment. Defining what level of quality a software service should publish in the registry is a big challenge because of (i) the lack of requestor's QoS requirements when a service is firstly published, (ii) the dynamic, diversified QoS requirements of SLAs (Service Level Agreement) and invocation instances to the same service provider, and (iii) the inability of requestors to precisely specify their QoS requirements for the services they demand. In this paper, we propose a mechanism to automatically recommend the QoS requirements of a given service by referencing previously signed SLAs and their associated runtime instance information of all "similar services" within a service community. Both the mathematical model and its supporting system architecture are given. This work is important because it assists service providers to improve their service quality and competitiveness in a given service community.
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