What is the difference between the Companion of the SOEP-Core and the SOEP-IS?

Since the data of the SOEP-Core and SOEP-IS are largely similar, but the SOEP-Core-Companion was created first, it contains a lot of content that also applies to SOEP-IS (e.g. the Missing-Conventions). The SOEP-IS Companion mainly offers information on deviating processes or data that are only relevant in SOEP-IS. It is moreover explicitly directed at the authors and users of the innovative modules.