There is no need to route the request event through the XslProcessingEditor because the necessary object trees could not be produced. Last, there is the case in which the XML and XSL sources are well-formed and the XslProcessingEditor was invoked, but XSL processing failed. All these images are simplified illustrations of a Meg chain. For clarity and simplicity default Megs and Megs of other plugins were omitted. Theoretically, all this functionality could have been implemented in just one Meg.
Small Megs are easier to change, modify and debug.
Well defined Megs can be reused in other applications. This makes changing things easier than working with a single, monolithic aaplication. Contains the class definition of the Stylesheet Identification Editor. Contains the class definition of the XML Error Editor. Contains the class definition of the XSL Processing Editor.