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Title

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1		-[Layout] New Crossing Minimization strategies for ELK and their use for SCCharts
	1	+Node Placement with Flexible Node Size and Port Position

Author

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1		-XWiki.sdo
	1	+XWiki.stu230980

Content

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1		-There exist many one-sided crossing minimization strategies such as the Barycenter heuristic [1], the median heuristic [2], as well as sifting [3].
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3		-The Eclipse Layout Kernel currently supports only the Barycenter heuristic, as well as the greedy switch heuristic [4].
	2	+The classic Sugiyama graph drawing algorithm consists of 5 phases: cycle breaking, layer assignment, crossing minimization, node placement and edge routing. Node placement sets the x-coordinates of nodes (in a downward layout) and creates alignment between nodes, improves edge straightness, or balances nodes based on their incoming edges. Node sizes can also be used to eliminate edge bends by increasing the size of nodes, as seen below, which makes the drawing easier to read, edges easier to follow and therefore easier to understand.
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5		-Part of this thesis should be to implement, new crossing minimization strategies and compare them based on the SCCharts language and its models.
	4	+[[image:attach:jette-stpa-oyes-bad.png]]
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	6	+[[image:attach:jette-stpa-oyes.png]]
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	8	+Figure showing the current layout without flexible node size and the existing ONO (obviously not optimal) parts of a layout with flexible node size
	9	+
7	7	= Goals =
8	8
9		-* Implement already existing crossing minimization strategies in ELK
10		-* Evaluate their use for a SCCharts
	12	+* Improve the existing Network Simplex node placement strategy with flexible node size by:\\
	13	+** centering edges on their nodes if it does not compromise the quality of the layout, if necessary by increasing node sizes even more
	14	+** minimize the size of the drawing if possible
	15	+* (optional) Explore options that need configuration depending on the context.
	16	+** alignment of edges, ...
11	11
12	12	= Scope =
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15	15
16	16	= Related Work/Literature =
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18		-1. K. Sugiyama, S. Tagawa, and M. Toda. Methods for visual understanding of hierarchical system structures. IEEE Transactions on Systems, Man and Cybernetics, 11(2):109–125, February 1981.
19		-1. P. Eades and S. Whitesides. Drawing graphs in two layers. Theoretical Computer Science, 131:361–374, 1994
20		-1. Matuszewski, Christian, Robby Schönfeld, and Paul Molitor. "Using sifting for k-layer straightline crossing minimization." //Graph Drawing: 7th International Symposium, GD’99 Štiřín Castle, Czech Republic September 15–19, 1999 Proceedings 7//. Springer Berlin Heidelberg, 1999.
21		-1. P. Eades and D. Kelly. Heuristics for reducing crossings in 2-layered networks. Ars Combin., 21.A:89–98, 1986.
	24	+Emden R. Gansner, Eleftherios Koutsofios, Stephen C. North, Kiem-Phong Vo, //A technique for drawing directed graphs//. Software Engineering 19(3), pp. 214-230, 1993.
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	26	+Ulf Rüegg, //Sugiyama Layouts for Prescribed Drawing Areas //([[KCSS>>url:https://www.uni-kiel.de/journals/receive/jportal_jparticle_00000341||shape="rect" class="internal-link"]] 2018/1), Chapter 4.1: Network Simplex Approach
	27	+
23	23	= Involved Languages/Technologies =
24	24
25	25	* Java
26	26	* ELK
	32	+** [[https:~~/~~/github.com/eclipse/elk/issues/853>>url:https://github.com/eclipse/elk/issues/853||shape="rect"]] (corresponding ticket in [[ELK>>url:https://www.eclipse.org/elk/||shape="rect"]])
27	27
28	28	= Supervised By =
29	29
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30	30	Sören Domrös
31	31
32	32	sdo@ifi
	39	+