What is inside-out modelling? It is a design paradigm that takes a business component and models it so that it can be exposed as a service. The entities and properties thereof are generally driven by the component interface. The most common form of inside-out driver is the RFC function module, although BOR objects and others like GENIL are available.
This is in contrast to outside-in model design , where the service that is required is modelled and the appropriate backend components are located or built to serve the consumption model.
The important phrase for me is “to serve the consumption model”; conversely, inside-out design can be paraphrased as “a service imposed by the business model”. Gateway consumers should not really be concerned with or know about the business model; it is generally a lot bigger and more complex than a particular service use case would need.
I am not a huge advocate of inside-out modelling but where it is deemed necessary, it can often be improved to work in a Gateway OData service context.
I’ve written a full blog on this subject but it is posted in the “other” Gateway space because I’m a developer at heart. However it does cover some design topics that would be of interest to non-developers so here is the link.