SAN FRANCISCO (AP) — Apple is expected to reveal a digital radio service and changes to the software behind iPhones and iPads today as the company opens its annual conference for software developers.Apple hasn’t said what it will unveil at the Worldwide Developers Conference in San Francisco. But the major announcements are expected during Monday’s keynote presentation. Last year, Apple used the conference to announce its own mapping service, better integration with social networks and improvements to virtual assistant Siri.