How an idea grows from birth on the back of a bar napkin to maturity in a market.

THE annual "hype cycle" chart from Gartner, a market research firm, tries to depict the degree to which certain technologies are exaggerated. Smart robots? Don't hold your breath. Big data? Not yet. In the firm's view, innovation advances in stages: from exuberance to pessimism to adoption. Not every technology progresses at the same speed, so Gartner assigns each an estimated time until the end of its ride.

Of course the chart presumes that innovations follow a set pattern, from bar napkin to mass market, which is a simplification. And wags can complain about certain placements: cloud computing is making transformative contributions to business and science in the form of Amazon's data-processing services, Salesforce's customer-management platform and Google docs. But Gartner bizarrely places it in a trough.

The Gartner hype cycle is, itself, rather hyped. Fittingly, our chart gives it a little more exposure still, and links many emerging technologies to stories in the newspaper. For a look at how innovations evolve over time, read this week's Difference engine column here.