But industry executives cited subtle differences Thursday at the SIAA (Software & Information Industry Association) OnDemand 2009 conference in San Jose, Calif., during a panel session pertaining to cloud computing, business models, and the enterprise.

Panelists spoke of the cloud and SaaS as separate entities. Treb Ryan, CEO of cloud infrastructure provider OpSource, for example, stressed that "service levels of what we've seen in the cloud so far are far worse than [we have] seen from any SaaS provider."

Asked the differences between SaaS and cloud computing, Ryan and IBM's Dave Mitchell, director of strategy and emerging business for ISV and developer relations, cited nuanced differences.

"Some people view SaaS as a layer within cloud computing," Mitchell said. He also noted, "[SaaS is] really about delivering an application on a subscription model over the Internet."