Patchwork is an extension to the Apache Cocoon framework which gives you the possibility to define and inherit layouts. This is similar to the Struts plugin Tiles, but adjusted to the requirements for using such a technique within Apache Cocoon.
The term layout definition or in short layout in Patchwork is defined by the following items:
Patchwork allows you to define the structure of your layouts in one central place. Therefore if you wan't to create a new layout or if you configure existing layouts you can do it within one single xml document. This makes it much more easier for you to get an overview of the websites layout structure and to introduce new layouts.
Depending on the layout you would like to load, Patchwork merges them together for you, without the need of writing any Controller and merge logic. And sure, there is nothing that speaks against adding additional Controllers if you want to do so!
Once you have created your additional layout structure you can inherit from other layouts as well. Doing it this way allows you to avoid redundancy and makes your work much more faster and productively!
Using the PatchworkGenerator, Patchwork can cache all merged layouts. This can improve the performance drastically! (Currently not implemented, but in the pipeline.)