The Journal's Shira Ovide places the move in the context of the newspaper industry–wide drive toward creating more premium-content products to generate revenues that will replace lost advertising dollars. Murdoch has been among the industry's most vocal proponents of charging readers to access online news.

But there's more going on than just that. It's also News Corp. (NWS)'s way of breaking off a bigger piece of the lucrative professional-data business that Bloomberg and Thomson-Reuters (TRI) now dominate. As I noted yesterday, installations of Bloomberg Professional terminals are up this year, despite the massive job losses in the financial sector -- a sign that the data business is a lot sturdier than ad-supported consumer media.

Reuters' Robert MacMillan says Wall Street Journal Professional is calculated to appeal to a forgotten middle class of business-news consumers. "The Journal is trying to capture readers for whom paper is not enough," he says, "while financial professional-grade data feeds offer too much at too high a price, and don't look all that pleasing to the eye." For his part, economics writer Felix Salmon puckishly Tweets: "Does this mean that the newspaper is The Wall Street Journal Amateur Edition?"

In hindsight, it seems Journal managing editor Robert Thompson was hinting at the launch of WSJ Professional when, in March, he riled up some underlings with a memo calling for them to generate more scoops. Thompson's memo noted that the "same story can be repurposed for a range of different audiences" and argued: "Not all content demands to be free and our content, in particular, has a value that is sometimes better recognised by our readers than our journalists. That we have multiple opportunities to generate income from this content is in stark contrast to many other revenue-challenged news organizations."