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Changes for page KLay Layered

Last modified by Richard Kreissig on 2023/09/14 10:18
From version 26.1
edited by sskr2
on 2023/07/06 14:36
Change comment: Renamed from xwiki:KIELER.KLay Layered
To version 24.1
edited by uru
on 2015/03/12 15:33
Change comment: There is no comment for this version

Summary

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1 -Layout Algorithms (KLay)
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1 -XWiki.sskr2
1 +XWiki.uru
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1 1  {{panel title="Project Overview" borderStyle="dashed"}}
2 2  Responsible:
3 3  
4 -* {{mention reference="XWiki.cds" style="FULL_NAME" anchor="XWiki-cds-tQPgJ"/}}
4 +* {{mention reference="XWiki.cds" style="FULL_NAME" anchor="XWiki-cds-WDonl"/}}
5 5  
6 6  Key Publications:
7 7  
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43 43  
44 44  The backbone of KLay Layered are its five layout phases, of which each is performing a specific part of the work necessary to layout a graph. Three of the five phases (layer assignment, crossing minimization, and node placement) go back to a paper by Sugiyama et al. They are widely used as the basis for layout algorithms, and can be found in loads of papers on the topic. A detailed description of what each layout phase does can be found [[on this page>>doc:The Five Phases]].
45 45  
46 -Intermediate processors are less prevalent. In fact, they are one of our contributions to the world of layout algorithms. The idea here is that we want KLay Layered to be as generic as possible, supporting different kinds of diagrams, laid out in different kinds of ways (as long as the layout is based on layers). Thus, we are well motivated to keep the layout phases as simple as possible. To adapt the algorithm to different needs, we then introduced small processors between the main layout phases (the space between two layout phases is called a //slot//). One processor can appear in different slots, and one slot can be occupied by more than one processor. Processors usually modify the graph to be laid out in ways that allow the main phases to solve problems they wouldn't solve otherwise. That's an abstract enough explanation for it to mean anything and nothing at once, so let's take a look at a short example.
46 +Intermediate processors are less prevalent. In fact, they are one of our contributions to the world of layout algorithms. The idea here is that we want KLay Layered to be as generic as possible, supporting different kinds of diagrams, laid out in different kinds of ways. (as long as the layout is based on layers) Thus, we are well motivated to keep the layout phases as simple as possible. To adapt the algorithm to different needs, we then introduced small processors between the main layout phases. (the space between two layout phases is called a //slot//) One processor can appear in different slots, and one slot can be occupied by more than one processor. Processors usually modify the graph to be laid out in ways that allow the main phases to solve problems they wouldn't solve otherwise. That's an abstract enough explanation for it to mean anything and nothing at once, so let's take a look at a short example.
47 47  
48 -The task of phase 2 is to produce a layering of the graph. The result is that each node is assigned to a layer in a way that edges always point to a node in a higher layer. However, later phases may require the layering to be //proper (a layering is said to be proper if two nodes being connected by an edge are assigned to neighboring layers)//. Instead of modifying the layerer to check if a proper layering is needed, we introduced an intermediate processor that turns a layering into a proper layering. Phases that need a proper layering can then just indicate that they want that processor to be placed in one of the slots.
48 +The task of phase 2 is to produce a layering of the graph. The result is that each node is assigned to a layer in a way that edges always point to a node in a higher layer. However, later phases may require the layering to be //proper//. (a layering is said to be proper if two nodes being connected by an edge are assigned to neighboring layers) Instead of modifying the layerer to check if a proper layering is needed, we introduced an intermediate processors that turns a layering into a proper layering. Phases that need a proper layering can then just indicate that they want that processor to be placed in one of the slots.
49 49  
50 50  For graphs that are not connected it is possible to execute the algorithm, i.e. the five phases with intermediate processors, separately on each connected component. The connected components processor splits an unconnected graph into multiple connected graphs and rearranges them after the layout of each component has been computed. This helps to present the components more compactly and neatly.
51 51  
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63 63  
64 64  [[image:attach:Layering_Dummies.png]]
65 65  
66 -In KLay Layered, we make extensive use of dummy nodes to reduce complex and very specific problems such that we can solve them using our general phases. One example is our implementation of port support on the northern or southern side of a node.
66 +In KLay Layered, we make extensive use of dummy nodes to reduce complex and very specific problems such that we can solve them using our general phases. One example is how we have implemented support for ports on the northern or southern side of a node.
67 67  
68 68  == Class Design ==
69 69  
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93 93  
94 94  The central class is the LayeredLayoutProvider. It does the following:
95 95  
96 -1. Using one of the IGraphImporter implementations, it imports the KGraph to be laid out into KLay Layered's LGraph format. Which implementation is used depends on whether the algorithm has to compute a layout for all hierarchy levels at once (compound layout) or not.
96 +1. Using one of the IGraphImporter implementations, it imports the KGraph to be laid out into KLay Layered's LGraph format. Which implementation is used depends on whether the algorithm has to compute a layout for all hierarchy levels at one (compound layout) or not.
97 97  1. Since the algorithm's configuration depends on the graph to be laid out, the LayeredLayoutProvider now has to decide which ILayoutPhase implementations to use for each of the five layout phases (this is specified with the different phase strategy enumerations). Once that is decided, each ILayoutPhase is queried for an IntermediateProcessingConfiguration, which describes – using the LayoutProcessorStrategy – the ILayoutProcessors it needs in each of the intermediate processing slots. The outcome of this step is a list of ILayoutProcessor instances that constitute the concrete layout algorithm.
98 98  1. Next, the imported graph is split into its connected components using the ComponentsProcessor. The processor does the work of splitting the graph into its connected components.
99 99  1. The main step: executing the algorithm (the list of ILayoutProcessor instances, as you will certainly remember) on each connected component.
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1 -884878
1 +10751773
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1 -https://rtsys.informatik.uni-kiel.de/confluence//wiki/spaces/KIELER/pages/884878/KLay Layered
1 +https://rtsys.informatik.uni-kiel.de/confluence//wiki/spaces/KIELER/pages/10751773/KLay Layered
XWiki.XWikiComments[0]
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1 -XWiki.marvin
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1 -The links to the papers and theses result in a 404 error. Will they be updated?
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1 -2015-08-24 16:58:39.0
XWiki.XWikiComments[1]
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1 -XWiki.uru
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1 -Thanks for mentioning this. We restructured our server landscape. Should be fixed now.
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1 -2015-08-24 17:42:20.0
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