Unstructured data is textual or non-textual data that is not in a database.
“Math-loving traders are using powerful computers to speed-read news reports, editorials, company Web sites, blog posts and even Twitter messages — and then letting the machines decide what it all means for the markets.
Many of the robo-readers look beyond the numbers and try to analyze market sentiment, that intuitive feeling investors have about the markets. Like the latest economic figures, news and social media buzz — ‘unstructured data,’ as it is known — can shift the mood from exuberance to despondency.”
See article at: NYT 23Dec10: “Computers That Trade on the News”