Steve Jobs, Apple chief executive, is getting a break from medical leave on Monday to take the chair over the opening of the annual conference of the company for software developers.

In a break from normal practice of the Apple of mantling its occasions in an air of mystery, the California device-manufacturer this time exposed prior to time what it plans to proclaim at the occasion in San Francisco.

Jobs and more executives will reveal the next generation of Lion, the software that powers Macintosh computer, and iOS 5, the following edition of the mobile operating system for the iPad, iPhone and iPod Touch, Apple said in a press release.

Apple illustrated the formerly unidentified iCloud as its “upcoming cloud services offering” but offered no further details of what expects at the yearly Worldwide Developers Conference.

Michael Gartenberg, an analyst for technology research company Gartner said, “iCloud was almost a throwaway line in the press release.  But that’s getting the most scrutiny because we don’t know anything about it.”

iCloud would let for streaming of music hosted on Apple servers in the Internet “cloud” to several gadgets from computers to smartphones to touchscreen tablets, according to several reports.

iCloud will partly be presented for free to iTunes users, letting them to pay attention to music hosted on Apple servers on a Web browser or an Internet-linked Apple gadget.

According to the newspaper, Apple will finally charge a subscription fee of about $25 per year for the service.

Amazon opened a Cloud Drive and Cloud Player music service in late March that permits subscribers to upload digital music to Amazon servers and play it on a computer or an Android gadget.

In May music service of Google introduced allows people store their music collection in online libraries for streaming to computers, smartphones and tablets.

On the other hand, Google Music does not sell songs and cloud service of Amazon needs time-consuming uploading of every song to Amazon servers before a user could listen to it.

Gartenberg anticipates an Apple service would “provide consumer value, differentiation from what’s come before and a way of taking the market forward.”

He asked, “What is going to be that extra Apple bit of magic that’s going to be infused that will drive consumers to use this?”

He said, “Apple was not the first company to offer downloads of music.  But they did it the best and therefore conquered the market. They weren’t first with MP3 players or smartphones.”

He added that iCloud might not be limited to music.

He said, “It could be synchronization for all my files — it could involve video, my office files.  I think what we’re going to see is something more than just another digital locker, another online storage place.”

He added, “It will be interesting to see if new business models are introduced.  If we’re talking about new ways to purchase, rent, listen to music, and share.”

Gartenberg said, “Anything they do that would be commerce-related is going to be fairly low friction if you’re already part of the iTunes ecosystem.”

It was improbable that Apple planned to expose a latest iPhone even though Jobs, a cancer survivor who went on medical leave in January for a secret illness, is recognized to love surprises.

Gartenberg said, “The fact that Apple telegraphed that this is going to about Lion, iOS 5, iCloud seems to me to downplay any expectation of new hardware. This is going to be very software-centric.”