Aggregate the values from an InfoPath repeating section for data administration

A common requirement for setting up (web)forms is to enter multiple rows of similar information. For example, entering the name(s) of your child(ren) for an holiday booking. The InfoPath Repeating Section enables an intuitive usage model for this. Initial the form displays only 1 section for data entrance. Via a link or button the user can on-the-fly expand the form with more occurrences of that same section.

Question is how best to administer the entered data from the repeating section in a SharePoint library. Is this a Master/Slave relationship? Or should it be considered simple as embedded in the form data self? The former requires a relation data model employed within the SharePoint information architecture. Although possible, this is not the typical SharePoint model which is namely to administrate the entity data in a single List or Library. However, for the second alternative it is still required to potentially administrate multiple values per field in the repeating section.

SharePoint supports this via the concept of AggregateFunction at Field level. To collect the data from a repeating section, specify aggregate="merge" for the field within the InfoPath form template

When explicitly self-provision the SiteColumns and ContentType (Administrate data from InfoPath form in a self-provisioned ContentType), you ran into a problem here. The FieldSpecification CAML currently does not allow the Aggregate attribute as in:

<FieldRef
  ID="{5e046132-9284-4322-b1c7-9a742d60270e}"
  Name="FirstNameChild"
  ReadOnly="TRUE"
  Node="/my:myFields/my:group/my:Children/my:FirstNameChild" />

SharePoint will fail the activation of your Feature with the error message: The 'Aggregation' attribute is not allowed.
The remedie is to skip the 'Aggregate' attribute from the CAML specification, and afterwards add it via an EventReceiver to the provisioned SPField in the RootWeb:

  SPField aggregateField = site.RootWeb.Fields[new Guid("{5e046132-9284-4322-b1c7-9a742d60270e}")];
  aggregateField.AggregationFunction = "merge";
  aggregateField.Update();