Putting it all together

Here's the complete code for this scenario solution:

Figure 1. Complete listing for a façade "list children" method

// ...
  @Inject
  private SomeParentDAO someParentDAO;

  public SomeChildSummaryDetailsList listSomeChildDetails(
      final SomeParentKey key)
      throws AppException, InformationalException {

    // create an instance of the return struct
    final SomeChildSummaryDetailsList list =
      new SomeChildSummaryDetailsList();

    // retrieve the instance of the parent entity
    final SomeParent someParent =
      someParentDAO.get(key.someParentID);

    // retrieve all the child instances of the entity for this
    // parent
    final Set<SomeChild> someChildren =
      someParent.getSomeChildren();

    // map the details returned
    for (final SomeChild someChild : someChildren) {
      final SomeChildSummaryDetails someChildSummaryDetails =
        new SomeChildSummaryDetails();
      someChildSummaryDetails.someChildID = someChild.getID();
      someChildSummaryDetails.name = someChild.getName();

      list.details.addRef(someChildSummaryDetails);
    }

    // return to the client
    return list;
  }

  // ...

Again, here is a briefer version which has no intermediate variable to hold the Set of child entity instances:

Figure 2. Complete listing for a façade "list children" method (terser version)

// ...
  public SomeChildSummaryDetailsList listSomeChildDetails(
      final SomeParentKey key)
      throws AppException, InformationalException {

    // create an instance of the return struct
    final SomeChildSummaryDetailsList list =
      new SomeChildSummaryDetailsList();

    // retrieve the instance of the parent entity
    final SomeParent someParent =
      someParentDAO.get(key.someParentID);

    for (final SomeChild someChild : someParent.getSomeChildren()) {
      // map the details returned
      final SomeChildSummaryDetails someChildSummaryDetails =
        new SomeChildSummaryDetails();
      someChildSummaryDetails.someChildID = someChild.getID();
      someChildSummaryDetails.name = someChild.getName();

      list.details.addRef(someChildSummaryDetails);
    }

    // return to the client
    return list;
  }
  // ...