4. Available data

The diversity of available data is now very wide, in terms of sectors of activity, the nature of the information and the media and means of access [9] .

The three main factors are not independent. For example, bibliographic data covers broad sectoral or multidisciplinary fields, while numerical or factual data corresponds to specific domains. Similarly, image processing is more often carried out locally (CD-ROM) than online, given transmission speeds, but here the situation is evolving very rapidly.

Currently, the number of online databases worldwide reported by the American Gale Directory exceeds 5,000, and growth over the last 15 years has been very rapid, although it is currently tending to decrease in intensity (figure