In discussion with @mcginkel it is clear that for progress and results to be exchanged, the LMS and LA need to agree a basic level of structure about the product itself to enable this exchange to happen.
Atomic: It needs to support the simplest model - e.g. the LA is a single activity (e.g. it starts, finishes, and has a result that is passed back) - like a typical LTI exchange.
MultiStep: It needs to support more complex models - e.g. the LA provides a set of activities or assignments that the learner can progress through over time, so progress and results should be exchanged about the activities.
In discussion with @mcginkel it is clear that for progress and results to be exchanged, the LMS and LA need to agree a basic level of structure about the product itself to enable this exchange to happen.
The basic catalogue is defined: https://stichtingsem.stoplight.io/docs/sem-technology-prototype/branches/learning-application-catalogue/reference/catalogue.v1.yaml for commercial usage (e.g. so a school can see, select, purchase).
The LMS requires more detail, thoughts:
Related: https://github.com/stichtingsem/technology-prototype/issues/17#issuecomment-673548511