Preserving Order during Crossing Minimization in Sugiyama Layouts

The Sugiyama algorithm, also known as the layered algorithm or hierarchical algorithm, is an established algorithm to produce crossing-minimal drawings of graphs. It does not, however, consider an initial order of the vertices and edges. We show how ordering real vertices, dummy vertices, and edge ports before crossing minimization may preserve the initial order given by the graph without compromising, on average, the quality of the drawing regarding edge crossings. Even for solutions in which the initial graph order produces more crossings than necessary or the vertex and edge order is conflicting, the proposed approach can produce better crossing-minimal drawings than the traditional approach

A Case-Study on Manual Verification of State-based Source Code Generated by KIELER SCCharts

Statecharts-like languages, such as SCCharts, are commonly used to develop stateoriented reactive and critical systems. Code is often generated by automatic code generators, which employ different strategies. This paper presents the results of a second user study on manual user verification of different source codes, which were generated using a netlist-based, a priority-based, and a state-based code generation approach compiling SCCharts models to C. The evaluation shows that manual verification can be time-consuming and is error prone if the user has no clear mapping between states and transition of the original model and the generated code. The participants performed better if the generated code followed a state pattern that preserves original model structures and names

SCCharts: The Mindstorms Report

SCCharts are a visual language proposed in 2012 for specifying safety-critical reactive systems. This is the second SCCharts report towards the usability of the SCCharts visual language and its KIELER SCCharts implementation. KIELER is an open-source project which researches the pragmatics of model-based languages and related fields. Nine case-studies that were conducted between 2015 and 2019 evaluate the pros and cons in the context of small-scale Lego Mindstorms models and similar projects. Par-ticipants of the studies included undergraduate and graduate students from our local and also external facilities, as well as academics from the synchronous community. In the surveys, both the SCCharts language and the SCCharts tools are compared to other modeling and classical programming languages and tools

Terrestrial and aquatic responses to climate change and human impact on the southeastern Tibetan Plateau during the past two centuries

Rapid population growth and economic development have led to increased anthropogenic pressures on the Tibetan Plateau, causing significant land cover changes with potentially severe ecological consequences. To assess whether or not these pressures are also affecting the remote montane-boreal lakes on the SE Tibetan Plateau, fossil pollen and diatom data from two lakes were synthesized. The interplay of aquatic and terrestrial ecosystem response was explored in respect to climate variability and human activity over the past 200 years. Nonmetric multidimensional scaling and Procrustes rotation analysis were undertaken to determine whether pollen and diatom responses in each lake were similar and synchronous. Detrended canonical correspondence analysis was used to develop quantitative estimates of compositional species turnover. Despite instrumental evidence of significant climatic warming on the southeastern Plateau, the pollen and diatom records indicate very stable species composition throughout their profiles and show only very subtle responses to environmental changes over the past 200 years. The compositional species turnover (0.36-0.94 SD) is relatively low in comparison to the species reorganizations known from the periods during the mid-and early-Holocene (0.64-1.61 SD) on the SE Plateau, and also in comparison to turnover rates of sediment records from climate-sensitive regions in the circum arctic. Our results indicate that climatically induced ecological thresholds are not yet crossed, but that human activity has an increasing influence, particularly on the terrestrial ecosystem in our study area. Synergistic processes of post-Little Ice Age warming, 20th century climate warming and extensive reforestations since the 19th century have initiated a change from natural oak-pine forests to seminatural, likely less resilient pine-oak forests. Further warming and anthropogenic disturbances would possibly exceed the ecological threshold of these ecosystems and lead to severe ecological consequences