BRUSSELS (Reuters) - EU antitrust regulators on Thursday launched proceedings to ensure that Apple ( AAPL ) complies with landmark rules requiring it to open up its closed ecosystem to rivals.

Under the so-called specification proceedings, the European Commission will spell out what Apple ( AAPL ) has to do to abide by the Digital Markets Act.

"The first proceeding focuses on several iOS connectivity features and functionalities, predominantly used for and by connected devices," the EU competition enforcer said.

"The second proceeding focuses on the process Apple ( AAPL ) has set up to address interoperability requests submitted by developers and third parties for iOS and IPadOS," it said.