Since the existence of a parent-child relationship, they certainly are called sub-components in the parent assembly.
And the data transmitted to the parent sub-assembly components, can be defined on a sub-assembly properties, to pass data from the attribute is defined in a manner to achieve the data transfer to the parent component subassembly.
In fact, the parent component references subassembly, the function similar to the data call, transmitted to the parent component sub-assembly, similar to the arguments passed to the function; required parameter definitions and default values in the other subassembly.
For example:
1, calls the sub-assembly in the parent assembly A:
2, the subassembly defined in subassemblies:
