Please correct me if I'm wrong and sorry if my question sounds confusing.
I heard that ETL Studio uses XML as its file type when exporting jobs/etc while DI Studio's saves it as an .spk file. What is the structure of the XML file back then on ETL Studio's era? And why was the save as XML file when exporting metadata removed in DI Studio?
You may want to consider opening a SAS Support tracking issue to address your SAS architecture questions - I noticed that the SAS DI Studio 3.4 Guide has the paragraph pasted below, regarding exporting metadata (Chapter 4, page 67):
For more information about the export and import of whole metadata repositories,
administrators should see the metadata management chapters in the SAS Intelligence Platform: System Administration Guide, especially the "Creating, Moving, Copying, and Deleting Metadata Repositories" chapter.
This might be a bit confusing.
As a part of the concept partial promotion, they created the Export/Import Wizards, which as you notice is a compressed package file. The package file itself contains a XML-file, a log and an extra file I don't really know what is used for. These can only be used within SAS environments, I guess, since job/process definition are very SAS specific.
Still, there is a tool called Metadata Exporter/Importer (reached from the Tool menu) which can be used if you plan to share metadata between SAS and other products such as ERwin, external DBMS etc. These files are XML as well, using the Common Warehouse Metamodel standard.