This question already has an answer here:

I'm looking for a straightforward answer that actually works...not a 'duplicate question' flag. None of the other solutions posted in similar threads actually work...they all have dead-end answers and/or links. I've searched for hours and spent many more actually trying the methods I've found and none seem to work.

As for my question; I'm looking to generalize the polygons of a shapefile to reduce their resolution. Topology needs to be maintained for future geometry functions such as difference and union. There doesn't seem to be any way to preserve topology in QGIS...is there any other way? Any suggestions will help (as long as it doesn't involve ArcGIS).

Previous questions which don't have useful answers:

Simplifying Shapefile using ArcGIS Desktop or alternative? - topology is not considered

Generalizing polygon file while maintaining topology in QGIS? - no accepted answer

How to check Topology in QGIS?

Also another questions of mine:

Simplify by number of points in QGIS

marked as duplicate by underdark Dec 20 '14 at 18:34

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

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    It may help to add links to the questions/solutions you have already tried. This may help others to know what questions you have looked at and prevent them from flagging this as a duplicate. – landocalrissian Dec 19 '14 at 19:00
  • Do you mean multi-layers topology or only self topology? I have a solution with FME for both but I think you can reproduce it with another chain of treatement such in postgis or even QGIS maybe. – Below the Radar Dec 19 '14 at 19:25
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    See if arcgis solution will point you in a right direction. 1.convert topologically correct polygons to polylines. 2 planarise lines. 3. Generalise lines. 4. Build polygons from simplified lines/edges. Don't forget to transfer original polygon attributes to point shapefile, so that you can bring them back – FelixIP Dec 19 '14 at 23:03
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    When you say "doesn't work", it would be useful to know what happened instead. That might help to understand what is different between your situation and the situation in those questions. – BradHards Dec 20 '14 at 1:07
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    Please note that it does not improve the quality of this site to have two unanswered questions about the same issue. That's why I'm closing this as duplicate and putting a bounty on the older question to motivate answers. – underdark Dec 20 '14 at 18:34