The concept of code layers is that developers should be able to include code at a layer level without interfering with any other layers of code. It also separates code, so that it is easy to understand each layers interactions with the code.
In each layer, except for the base layer, it is possible to add layer specific code and to change the previous layers' code by creating an override or overtake of the code. Override of code means that you, in your layer add new functionality before or after a call to the previous layers' code. Overtake of a method means that you take the full responsibility of the code from this layer onwards.
In IFS Applications, there are three layers you can work with: Core, Ext, and Cust.
Core – The standard implementation layer delivered by IFS R&D containing all application logic. It cannot be edited and is used as a template for the other two layers; Ext and Cust. These layers can override the appropriate methods and change the standard core implementation.
Ext – The extension layer
This layer is the first layer that can be chosen, after the Core, and is meant to be used for all extensions of IFS Applications. An extension is typically IFS R&D development which originated as a request from several customers that in the future will be merged into the core product of IFS Applications.
Cust – The customization layer
This layer is the second (and currently the last) layer used to customize the client based on requests from a single customer.