Drawing directed graphs has many applications and occurs whenever a natural flow of information is to be visualized. Given a directed acyclic graph (DAG) G, we are interested in an upward drawing of G, that is, a drawing of G in which all arcs are drawn as curves that are monotonically increasing in the vertical direction. Besides the upward property, it is desirable that the number of arc cros...

We study the problem of Upward Point-Set Embeddability, that is the problem of deciding whether a given upward planar digraph D has an upward planar embedding into a point set S. We show that any switch tree admits an upward planar straight-line embedding into any convex point set. For the class of k-switch trees, that is a generalization of switch trees (according to this definition a switch t...

By a celebrated theorem of Morley, a theory T is א1-categorical if and only if it is κ-categorical for all uncountable κ. In this paper we are taking the first steps towards extending Morley’s categoricity theorem “to the finite”. In more detail, we are presenting conditions, implying that certain finite subsets of certain א1-categorical T have at most one n-element model for each natural numbe...

Abstract. Recently, we have presented a new practical method for upward crossing minimization [4], which clearly outperformed existing approaches for drawing hierarchical graphs in that respect. The outcome of this method is an upward planar representation (UPR), a planarly embedded graph in which crossings are represented by dummy vertices. However, straight-forward approaches for drawing such...

this comment argues that instead of worrying about the pros and cons of whistleblowing one should focus on the more general problem of the failure of upward communication around safety and quality problems and consider what leaders and managers must do to stimulate subordinates to communicate and reward such communication. the article analyzes why safety failures occur and introduces the concep...