Per the Esri Preparing Data for Offline Use (Enabling Sync on ArcGIS Server Feature Services) documentation, it states:
"Relationship Classes and Attachments MUST use GlobalID as the Primary Key"
However, when attempting to use AGSRelationshipQuery to query the related table, the parameters only allow the use of ObjectIds (via the NSArray objectIds property).
Can anyone provide clarification on this? Or an alternative method to querying related tables during offline use?