Understanding the app schema for using complex features in QGIS

Question

I'm working with complex features on the GeoServer and the app schema extension.

My understanding of the app-schema extension is that you are able to map complex features through a WFS at the end. In other words, the app-schema is the connecting element between your complex data and a GIS software which do the WFS request.

Or is the extensions only responsible to create a valid WFS response of the complex features and the visualization of them is another part of the story?

Example using QGIS and complex features
I will give you an example. Regarding to my previous question I'm working with the App Schema tutorial data 

When I load the WFS Layer in QGIS the mapping is wrong. Only one layer will be added with all information about the complex features. In addition, QGIS can not interpret the geometry (no data is displayed).

The only way to display the data is to use the GML Application Schema toolbox QGIS plugin.

When I am using the plugin, my complex features are stored in three separate layers and will be displayed successfully.

Versions:
QGIS: 3.2
GeoServer: 2.12.1
GML Application Schema plugin 1.2.0

Answer 1

GeoServer App schema, allows you to map your complex data to a schema, so that you can serve your data though a WFS (a complex feature WFS).

The WFS requests that come from the client (in this case QGIS) are the same as they would be for a simple feature WFS. In any WFS, the data is sent without any styling. It's the clients responsibility to parse the data response and apply style (or not) as required.

QGIS (out of the box) does not understand complex feature WFS responses, so you have to use a plugin.