The RSL reference manual has detailed discussion of object composition. Refining object definitions. An examination of the narrative for the event dialog, indicates that the Title and Location components of an event are free-form strings. In Milestone 4, the details of date formats has not yet been worked out. Given this, we'll leave the definitions of StartDate and EndDate to be resolved later.
Opaque objects are primitives similar to enumeration literals in a programming language.
The preceding analysis for deriving objects is typical in requirements modeling. First we derive initial object definitions from the UI pictures. Then we refine the definitions based on the scenario narrative. We continue to refine until all objects are defined in terms of primitives. Refining operation definitions.