I am posting this question regarding a term called "multiple coordinte system". I firstly see this term in ESRI ArcGIS Web Developer Certification guidnance, and it is shown as "Evaluate the impact of using multiple coordinate system". However, I feel confused here about this term "multiple coordinte system". Does it mean "Multiple" + "Coordinate systems", which from my understanding, e.g. geographic coordinate systems/projected coordinate systems. Or there is a concept callled "Multiple coordinate system" where a feature/asset can have multiple coordinate systems (multi coordinate system models) in the same time so they can change the coordinate on demand (for BIM etc?) I am looking forward for your answer.
It is referring to having different layers in the map with individually different coordinate systems. You can not define multiple coordinate systems for an individual file.