Head

---

The compose head can optionally define a name for the compose declaration. The purpose of this name is to improve the readability and documentation of the mapping schema, and to be able to refer to the compose declaration by name in the EDMmodelConverter^ log file. The compose name must be a unique identifier in the global scope of the mapping schema followed by the keyword FOR.
The extended entity reference defines the target instance type to iterate over, when the actual compose declaration is executed. The keyword SUBTYPE can optionally be specified before the extended entity reference, meaning that all instances that is a subtype of the instance specified by the extended entity reference will be added to the set of target instances to iterate over.
The compose head optionally defines a FROM clause in the same way as it is done in the Map Head. Instance types from both the source schema and the target schema can be listed in the FROM clause in a compose head. This FROM clause adds nested iterations for all combinations of instance types defined in the FROM clause, to the iteration specified by the compose instance. The WHEN clause terminates head declaration. This WHEN clause defines the conditions which must be met by the current combination of instances, in order to apply the statements listed in the compose body.